Re: [Tutor] decision loops
Hello Daniel, and welcome! On Sat, Jan 31, 2015 at 08:54:48PM -0500, Daniel M wrote: Hello. I'm a complete beginner and I’m trying to write a very basic script to convert temperatures, just for some practice. I have that part down, but I can’t figure out how to make the script switch between the two. What I would like it to do is let the user go back to the “What do you wish to convert?” part when a character is entered instead of a number for “temperature?”. I tried using elif m == *char* print (*What do you wish to convert to?*) temp = raw_input(* *) Why are there asterisks around parts of your code? That's a syntax error in Python. I'm guessing that you didn't type them yourself, and that your email program is doing it. You should set your email program to only send plain text, not Rich Text or formatted text or HTML or whatever silly thing it is trying to do. but it seems useless regardless of where I put it. It gives me the error “ return eval(raw_input(prompt)) In the code you show below, there is no mention of eval. So that is your first mistake: whether you intended to or not (I'm pretty sure it wasn't deliberate!) you are telling us falsehoods. The code you say you are running is not the code you are actually running. How can we tell what you are doing wrong when we cannot see what you are doing? Mistake number two is using eval. As a beginner, there are three rules you should remember about eval: (1) If you think you might need to use eval, you don't. (2) If you are positive that you really do need to use eval, you probably don't. (3) For experts only -- if you are sure that you need to use eval, you might. The problems with eval are: - its slow - its tricky to use right except for the simplest cases - it can be dangerous and introduce serious security holes in your code if you aren't careful File string, line 1, in module NameError: name 't' is not defined” when I enter a character. Mistake number three: I'm guessing that you didn't enter any old character. I'm guessing you entered 't' rather than 's' or '3' or '.' or some other character. Your mistake is to make us guess: when asking for help, you should tell us what you did specifically, not vaguely. In this case, I think I can reproduce your problem: py eval(raw_input(Enter a character: )) Enter a character: t Traceback (most recent call last): File stdin, line 1, in module File string, line 1, in module NameError: name 't' is not defined I don't get that error from any random character, only from t. If I type a different character, I get a different error. Why? Because of eval. You're telling Python to evaluate what you typed as if it were code: py eval(raw_input(Enter a character: )) Enter a character: len([1, 2, 3]) + 1000 1003 You don't need eval here. It does nothing useful. What you want is simply raw_input(prompt). Hope that helps. -- Steve ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
[Tutor] decision loops
Hello. I'm a complete beginner and I’m trying to write a very basic script to convert temperatures, just for some practice. I have that part down, but I can’t figure out how to make the script switch between the two. What I would like it to do is let the user go back to the “What do you wish to convert?” part when a character is entered instead of a number for “temperature?”. I tried using elif m == *char* print (*What do you wish to convert to?*) temp = raw_input(* *) but it seems useless regardless of where I put it. It gives me the error “ return eval(raw_input(prompt)) File string, line 1, in module NameError: name 't' is not defined” when I enter a character. I’m sure I’m missing something very obvious but I can’t seem to figure it out. Where am I going wrong? def *ftoc*(x): #Fahrenheit to Celsius x == float y = x-32.0 z = y * 5.0 return z //9.0 def *ctof*(x): #Celsius to Fahrenheit x == float y = x * 9.0 z = y // 5.0 return z + 32.0 print (*What do you wish to convert to?*) temp = raw_input(* *) while temp == *c* or temp == *f* and not temp == *q*: if temp == *c*: m = float(input(*temperature?*)) print ftoc(m) print *Celcius* elif temp == *f*: m = float(input(*temperature?*)) print ctof(m) print (*Farenheit*) elif temp == *q*: break ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] decision loops
On 01/02/15 01:54, Daniel M wrote: I can’t figure out how to make the script switch between the two. What I would like it to do is let the user go back to the “What do you wish to convert?” part when a character is entered instead of a number for “temperature?”. I tried using That's quite a complex task you've set yourself. You need to differentiate numbers and characters even though you read them all as characters from the users. It might be simpler just to keep the numeric and character processing separate for now. And maybe for good. Also your subject says 'decision loops' Those are two completely separate things. decisions are made using if/elif/else constructs loops are repetitions involving 'for' or 'while' constructs (and a few more advamced ones later) You probably need both to solve your problem but do not confuse or merge the two ideas in your mind. At this stage we appear to only be dealing with decisions. The loops can wait till later. elif m == *char* print (*What do you wish to convert to?*) temp = raw_input(* *) The asterisks don't make sense, I'm guessing your mail program put them in because you made it bold or some-such? Please always use plain text when sending code. However, we can't really make much sense of it even without asterisks because we have no context. We don't know what 'm' is, where it comes from etc. Also m == char only makes sense if you have defined a variable called char somewhere, again we can't see it. Or are you simply trying to explain that you want to test m to see if it is a character? Its not clear. Don't make us guess. but it seems useless regardless of where I put it. It gives me the error “ return eval(raw_input(prompt)) And that line doesn't seem to appear in your code anywhere? And its only a bit of an error message, please always send us the whole error because its full of useful information. File string, line 1, in module NameError: name 't' is not defined” when I enter a character. This suggests that you passed a 't' to eval. The 't' must have come from the raw_input() but again you didn't tell us that we have to guess. I assume you get a slightly differnt error if you enter, say, a 'v' or a 'w'? missing something very obvious but I can’t seem to figure it out. Probably but you aren't giving us enough specific detail to be able to help you reliably. def *ftoc*(x): #Fahrenheit to Celsius x == float y = x-32.0 z = y * 5.0 return z //9.0 x = float doesn't do anything useful here. It assigns a new name (x) to the float type convertion function. I'm guessing(again) that what you really meant was x = float(x) to force x to be a floating point number? Also // produces integer division. I'm pretty sure you want regular float division z/9.0 def *ctof*(x): #Celsius to Fahrenheit x == float y = x * 9.0 z = y // 5.0 return z + 32.0 Pretty much the same comments as above print (*What do you wish to convert to?*) temp = raw_input(* *) while temp == *c* or temp == *f* and not temp == *q*: if temp == *c*: m = float(input(*temperature?*)) print ftoc(m) print *Celcius* elif temp == *f*: m = float(input(*temperature?*)) print ctof(m) print (*Farenheit*) elif temp == *q*: break OK, Now we see where 'm' fits in, although your char test above is missing. Also we see you using input() instead of raw_input() That's nearly always a mistake. Its better to use raw_input() and then explicitly convert to the type you want(which you do here anyway) So use: m = float(raw_input(temperature?)) Finally you probably want the unit selection inside the while loop so try something like this skeleton code: while True: temp = raw_input(What do you wish to convert to?) if temp == 'q': break if temp == c: m = float(raw_input(temperature?)) print ftoc(m) print Celcius elif temp == f: m = float(raw_input(temperature?)) print ctof(m) print (Farenheit) -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
[Tutor] While loops
I am currently coding a 'text-based adventure game', and im having a bit of
trouble with while loops. Here is my code so far: #Text-based Adventure RPG
#The player travels through different towns and dungeons
#The overall goal of the game is simple; the player must make it to the final
town,
#Battling various monsters and overcoming several challenges along the
wayimport timeplayer_name = None
player_invent = [30]
emb_town_visit=None
YES='yes'
NO='no'
user_choice=None
plyr_location='Embark'
shopkeep_mny=100
shopkeep_invent=['Bronze Sword (10)','Steel Sword (100)','Rounded Shield
(10)','Kite Shield (50)','Medicine (5)','Mana Potion (5)'] class
Main_char(object):
A class for the main character object.
def __init__(self,name,invent,level=1,health=30,mana=15):
self.name=name
self.level=level
self.invent=invent
self.hp=health
self.mana=mana
print(\nYour journey begins here in Embark town,+self.name)
def __str__(self):
print(\nName: ,self.name, \nLevel: ,self.level, \nYour
inventory: ,self.invent)def town_chcklist(self):
A checklist showing a list of the towns the player has
already visited.
self.checklist=[]
if town1==YES:
self.checklist.append(town1) def use_item(item):
Allows the player to use an item in their inventory.
if item in ('Medicine','Mana Potion'):
Hero.invent.delete(item)
if item=='Medicine':
Hero.hp+20
elif item=='Mana Potion':
Hero.mana+10class Shopkeep(object):
A blueprint for the shopkeeper objects.
def __init__(self,inv,money):
self.inv=inv
self.money=moneydef __str__(self):
print(Shopkeeper: Here are my wares: \n\n,self.inv+. \nI
currently have,self.money,gold.) #Create the towns/ dungeons/ areas in
different functionsdef Embark():
The town in which the player begins there journey.
if emb_town_visit==None:
print(Welcome to Embark Town,player_name+!)while
True:
print(\n,hero)
print(
\n\t\tPress '1' to exit the town...
\n\t\tPress '2' to enter the local shop...)
user_choice=input('What would you like to do?: ')
if user_choice=='1':
shop()
continue
elif user_choice=='2':
if emb_town_visit==None:
print(\n\t\t\tAs you leave your home of Embark
Town, you look back with a smile, then proceed North.)
break
else:
print(\n\t\t\tThat is not a valid choice...)
continue
#The player has visited Embark Town
if emb_town_visit==None:
emb_town_visit=YES#Exit the function and change the
players location variable
return 'Left Embark Town',emb_town_visit def shop():
A generic shop that is placed in each town.
while True:
print(
\nWhat would you like to do?
\nPress '1' to buy an item...
\n...Press '2' to exit the shop...
\n...Or press '3' to ask about the town...)
user_choice=input()
if user_choice=='1':
print(Shopkeeper: Goodbye.)
break
elif user_choice=='2':
print(emb_shopkeep)
user_choice=None
print(Enter the name of the item you would like to
purchase.)
user_choice=title(input())
for item in emb_shopkeep.inv:
if user_choice in emb_shopkeep.inv:
message=handle_pur(user_choice)
print(message)
emb_shopkeep.inv.delete(user_choice)
else:
print(\n\t\t\tThat is not a valid
choice!)def handle_pur(item):
Handles purhchases made by the player in the shop.
if item=='Bronze Sword':
if Hero.invent[0] = 10:
Hero.invent[0]-10
Hero.invent.append(item)
msg='You now own a',item
elif Hero.invent[0] 10:
msg='You cannot afford that item.'
elif item=='Steel Sword':
if Hero.invent[0] = 100:
Hero.invent[0] - 100
Hero.invent.append(item)
msg='You now own a',item
Re: [Tutor] While loops
On 7/7/2012 5:57 AM myles broomes said...
I am currently coding a 'text-based adventure game', and im having a bit
of trouble with while loops. Here is my code so far:
Please paste in the traceback you're getting, and please set your mail
client program for plain text when posting. What I see here has the
indentation stripped out of your script so that before I can even test
your code I'll have to guess at how you have it indented, and I'm more
likely than you to get it right and may inadvertently fix your bug and
never know it even before getting a chance to see the bug.
Emile
#Text-based Adventure RPG
#The player travels through different towns and dungeons
#The overall goal of the game is simple; the player must make it to the
final town,
#Battling various monsters and overcoming several challenges along the way
import time
player_name = None
player_invent = [30]
emb_town_visit=None
YES='yes'
NO='no'
user_choice=None
plyr_location='Embark'
shopkeep_mny=100
shopkeep_invent=['Bronze Sword (10)','Steel Sword (100)','Rounded Shield
(10)','Kite Shield (50)','Medicine (5)','Mana Potion (5)']
class Main_char(object):
A class for the main character object.
def __init__(self,name,invent,level=1,health=30,mana=15):
self.name=name
self.level=level
self.invent=invent
self.hp=health
self.mana=mana
print(\nYour journey begins here in Embark town,+self.name)
def __str__(self):
print(\nName: ,self.name, \nLevel: ,self.level, \nYour inventory:
,self.invent)
def town_chcklist(self):
A checklist showing a list of the towns the player has already
visited.
self.checklist=[]
if town1==YES:
self.checklist.append(town1)
def use_item(item):
Allows the player to use an item in their inventory.
if item in ('Medicine','Mana Potion'):
Hero.invent.delete(item)
if item=='Medicine':
Hero.hp+20
elif item=='Mana Potion':
Hero.mana+10
class Shopkeep(object):
A blueprint for the shopkeeper objects.
def __init__(self,inv,money):
self.inv=inv
self.money=money
def __str__(self):
print(Shopkeeper: Here are my wares: \n\n,self.inv+. \nI currently
have,self.money,gold.)
#Create the towns/ dungeons/ areas in different functions
def Embark():
The town in which the player begins there journey.
if emb_town_visit==None:
print(Welcome to Embark Town,player_name+!)
while True:
print(\n,hero)
print(
\n\t\tPress '1' to exit the town...
\n\t\tPress '2' to enter the local shop...)
user_choice=input('What would you like to do?: ')
if user_choice=='1':
shop()
continue
elif user_choice=='2':
if emb_town_visit==None:
print(\n\t\t\tAs you leave your home of Embark Town, you look back with
a smile, then proceed North.)
break
else:
print(\n\t\t\tThat is not a valid choice...)
continue
#The player has visited Embark Town
if emb_town_visit==None:
emb_town_visit=YES
#Exit the function and change the players location variable
return 'Left Embark Town',emb_town_visit
def shop():
A generic shop that is placed in each town.
while True:
print(
\nWhat would you like to do?
\nPress '1' to buy an item...
\n...Press '2' to exit the shop...
\n...Or press '3' to ask about the town...)
user_choice=input()
if user_choice=='1':
print(Shopkeeper: Goodbye.)
break
elif user_choice=='2':
print(emb_shopkeep)
user_choice=None
print(Enter the name of the item you would like to purchase.)
user_choice=title(input())
for item in emb_shopkeep.inv:
if user_choice in emb_shopkeep.inv:
message=handle_pur(user_choice)
print(message)
emb_shopkeep.inv.delete(user_choice)
else:
print(\n\t\t\tThat is not a valid choice!)
def handle_pur(item):
Handles purhchases made by the player in the shop.
if item=='Bronze Sword':
if Hero.invent[0] = 10:
Hero.invent[0]-10
Hero.invent.append(item)
msg='You now own a',item
elif Hero.invent[0] 10:
msg='You cannot afford that item.'
elif item=='Steel Sword':
if Hero.invent[0] = 100:
Hero.invent[0] - 100
Hero.invent.append(item)
msg='You now own a',item
elif Hero.invent[0] 100:
msg='You cannot afford that item.'
elif item =='Rounded Shield':
if Hero.invent[0] = 10:
Hero.invent[0] - 10
Hero.invent.append(item)
msg='You now own a',item
elif Hero.invent 10:
msg='You cannot afford that item.'
elif item=='Kite Shield':
if Hero.invent[0] = 50:
Hero.invent[0] - 50
Hero.invent.append(item)
msg='You now own a',item
elif Hero.invent 50:
msg='You cannot afford that item.'
elif item=='Medicine':
if Hero.invent[0] = 5:
Hero.invent[0] - 5
Hero.invent.append(item)
msg='You now own a',item
elif Hero.invent[0] 5:
msg='You cannot afford that item.'
elif item=='Mana Potion':
if Hero.invent[0] = 5:
Hero.invent[0] - 5
Hero.invent.append(item)
msg='You now own a',item
elif Hero.invent[0] 5:
msg='You cannot afford that item.'
#Informs the program of which message to tell the player
return msg
emb_shopkeep=Shopkeep(shopkeep_invent,shopkeep_mny)
#Player creation loop
while True:
print(
\nValiant hero, your quest begins here in Embark Town.,
time.sleep(200),
\nWhere you will go is up to you...,
time.sleep(200),
\nHow your adventure will pan out is up to you...,
Re: [Tutor] While loops
On 07/07/12 13:57, myles broomes wrote:
I am currently coding a 'text-based adventure game', and im having a bit
of trouble with while loops. Here is my code so far:
What kind of trouble? You have lots of while loops, which loop?
And do you get an error message? If so please post it - all of it!
And looking through the code I see lots of potential problems, I have
highlighted a few below...
class Main_char(object):
def __init__(self,name,invent,level=1,health=30,mana=15):
def __str__(self):
def town_chcklist(self):
self.checklist=[]
if town1==YES:
self.checklist.append(town1)
This method always resets the list to empty and then appends town1.
You should move the initialisation of the list into __init__.
But I see no variable defined anywhere called 'town1' so you would
get an error... Fortunately you don't seem to call this method
so no error is ever produced...
def use_item(item):
Allows the player to use an item in their inventory.
if item in ('Medicine','Mana Potion'):
Hero.invent.delete(item)
if item=='Medicine':
Hero.hp+20
Here you add 20 to the value of Hero.hp but then throw thecresult away.
I suspect you mean:
Hero.hp += 20
elif item=='Mana Potion':
Hero.mana+10
What is Hero.mana? It does not appear in the MainChar class definition?
And as above I suspect you mean += 10?
class Shopkeep(object):
def __init__(self,inv,money):
self.inv=inv
self.money=money
def __str__(self):
print(Shopkeeper: Here are my wares: \n\n,self.inv+.
\nI currently have,self.money,gold.)
#Create the towns/ dungeons/ areas in different functions
def Embark():
Its usual practice to keep names startingt with a captial letter for
Clas names. It gets confusing for the reader(whio might be you!) otherwise.
The town in which the player begins there journey.
if emb_town_visit==None:
print(Welcome to Embark Town,player_name+!)
while True:
print(\n,hero)
print(
\n\t\tPress '1' to exit the town...
\n\t\tPress '2' to enter the local shop...)
user_choice=input('What would you like to do?: ')
if user_choice=='1':
shop()
continue
You don't need 'continue' here because the loop drops out here anyway.
But it won't do any harm.
elif user_choice=='2':
if emb_town_visit==None:
print(\n\t\t\tAs you leave your home
of Embark Town, you look back with a smile, then proceed North.)
break
else:
print(\n\t\t\tThat is not a valid choice...)
continue
same here. You only need continue if you are jumping out of the code
block back to the start of the loop. It should be a relatively rare
event in well structured code!
#The player has visited Embark Town
if emb_town_visit==None:
emb_town_visit=YES
#Exit the function and change the players location variable
return 'Left Embark Town',emb_town_visit
This is broken due to some bad use of variable names.
You define emb_town_visit as a global with value None.
First time into Embark you test the global and if its set to None you
*create a new local variable* of the same name. You then return it to
main which sets *yet another local variable* of the same name to YES.
But this does not change the global so next time you visit Embark the
global is still None and you go through the same routine. If you want to
use the global value (and especially if you want to change it) you must
specify it as global in each function . But frankly it should probably
not be global anyhow since you want to track that per player so it
should really be part of your character class.
def shop():
A generic shop that is placed in each town.
In that case it should probably be a class and you create an instance in
each town.
while True:
print(
\nWhat would you like to do?
\nPress '1' to buy an item...
\n...Press '2' to exit the shop...
\n...Or press '3' to ask about the town...)
user_choice=input()
if user_choice=='1':
print(Shopkeeper: Goodbye.)
break
elif user_choice=='2':
print(emb_shopkeep)
user_choice=None
print(Enter the name of the item you would
like to purchase.)
[Tutor] while loops
# Guess my number # # The computer picks a random number between 1 and 100 # The player tries to guess it and the computer lets # the player know if the guess is to high, to low # or right on the money import random print(\tWelcome to 'Guess My Number'!) print(I'm thinking of a number between 1 and 100.) print(Try to guess it in as few attempts as possible.\n) # set the initial values the_number = random.randint(1,100) guess = int(input(Take a guess: )) tries = 1 # Guessing loop while guess != the_number: if guess the_number: print(Lowere...) else: print(Higher...) guess = int(input(Take a guess: )) tries += 1 print(good job) input(\n\nPress the enter key to exit.) This is a program from Python for the absulute beginner(which I am). End of the chapter is a challenge that asks me to limit the number of guesses the player gets. If he/she fails to guess the number after a certain number of attempts then it displays a message about his failure.It needs to be a while loop cause it the topic I'm at.Can anyone give me some help on where to put the loop.When i put it in with the if guessthe_number loop, the program either prints higher or lower continuously(continuous loop I imagine) or it gives me the answer whether its right or wrong after a couple guesses.Any help will be appreciated. ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] while loops
rog capp wrote: [...] # Guessing loop while guess != the_number: if guess the_number: print(Lowere...) else: print(Higher...) guess = int(input(Take a guess: )) tries += 1 print(good job) input(\n\nPress the enter key to exit.) This is a program from Python for the absulute beginner(which I am). End of the chapter is a challenge that asks me to limit the number of guesses the player gets. If he/she fails to guess the number after a certain number of attempts then it displays a message about his failure.It needs to be a while loop cause it the topic I'm at.Can anyone give me some help You need a counter to count how many guesses are made. You already have a variable counting the number of tries, so you are half-way there. The loop condition currently is: while guess != the_number or in English: while the guess is not equal to the number: loop Still in English, you want to change the condition to: while the guess is not equal to the number and the number of tries is less than the maximum number of tries: loop Translate that loop condition from English to Python, and you've got it. Then, once you have the loop fixed, the final change needed is to change the message printed at the end, outside the loop. Currently it unconditionally prints good job. You need to change that to only print good job if the guess is equal to the number, otherwise print something else. -- Steven ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] while loops
On 12/14/2011 05:41 PM, rog capp wrote: # Guess my number # # The computer picks a random number between 1 and 100 # The player tries to guess it and the computer lets # the player know if the guess is to high, to low # or right on the money import random print(\tWelcome to 'Guess My Number'!) print(I'm thinking of a number between 1 and 100.) print(Try to guess it in as few attempts as possible.\n) # set the initial values the_number = random.randint(1,100) guess = int(input(Take a guess: )) tries = 1 # Guessing loop while guess != the_number: if guess the_number: print(Lowere...) else: print(Higher...) guess = int(input(Take a guess: )) tries += 1 print(good job) input(\n\nPress the enter key to exit.) This is a program from Python for the absulute beginner(which I am). End of the chapter is a challenge that asks me to limit the number of guesses the player gets. If he/she fails to guess the number after a certain number of attempts then it displays a message about his failure.It needs to be a while loop cause it the topic I'm at.Can anyone give me some help on where to put the loop.When i put it in with the if guessthe_number loop, the program either prints higher or lower continuously(continuous loop I imagine) or it gives me the answer whether its right or wrong after a couple guesses.Any help will be appreciated. _ You already have a while-loop. So add another condition to it: while guess != answer and tries 10: then outside the loop, write an if-test conditional on whether guess == number If so, tell him good job, if not, tell him he took too many tries. -- DaveA ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] while loops
On 14/12/11 22:41, rog capp wrote: # Guessing loop while guess != the_number: if guess the_number: else: guess = int(input(Take a guess: )) tries += 1 If he/she fails to guess the number after a certain number of attempts then it displays a message about his failure.It needs to be a while loop cause it the topic I'm at. Can anyone give me some help on where to put the loop. You already have one. Look at the code above, see the while? You do not need another one. And you are already counting how many times round the loop you go. So all you need to do is use that counter to stop the while loop when it reaches a given value. Currently the loop stops when guess == the_number You would like it to also stop when your counter reaches the limit. Do you know how to do that? Have a go and tell us how you get on. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] while loops
-Original Message- From: tutor-bounces+ramit.prasad=jpmorgan@python.org [mailto:tutor-bounces+ramit.prasad=jpmorgan@python.org] On Behalf Of rog capp Sent: Wednesday, December 14, 2011 4:41 PM To: tutor@python.org Subject: [Tutor] while loops # Guess my number # # The computer picks a random number between 1 and 100 # The player tries to guess it and the computer lets # the player know if the guess is to high, to low # or right on the money import random print(\tWelcome to 'Guess My Number'!) print(I'm thinking of a number between 1 and 100.) print(Try to guess it in as few attempts as possible.\n) # set the initial values the_number = random.randint(1,100) guess = int(input(Take a guess: )) tries = 1 # Guessing loop while guess != the_number: if guess the_number: print(Lowere...) else: print(Higher...) guess = int(input(Take a guess: )) tries += 1 print(good job) input(\n\nPress the enter key to exit.) This is a program from Python for the absulute beginner(which I am). End of the chapter is a challenge that asks me to limit the number of guesses the player gets. If he/she fails to guess the number after a certain number of attempts then it displays a message about his failure.It needs to be a while loop cause it the topic I'm at.Can anyone give me some help on where to put the loop.When i put it in with the if guessthe_number loop, the program either prints higher or lower continuously(continuous loop I imagine) or it gives me the answer whether its right or wrong after a couple guesses.Any help will be appreciated. = If you want to stop after a certain number of attempts, then your loop should compare the number of tries (you are storing this correctly) against the number of max allowed attempts (you are not storing this part so that needs to be done first). You can use the current loop, just change the conditions (this part is second)d. Hopefully that makes sense to you. Ramit Ramit Prasad | JPMorgan Chase Investment Bank | Currencies Technology 712 Main Street | Houston, TX 77002 work phone: 713 - 216 - 5423 -- This email is confidential and subject to important disclaimers and conditions including on offers for the purchase or sale of securities, accuracy and completeness of information, viruses, confidentiality, legal privilege, and legal entity disclaimers, available at http://www.jpmorgan.com/pages/disclosures/email. ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] nested loops
Alan Gauld wrote:- Wayne Werner waynejwer...@gmail.com wrote found = False highscore = 0 alignment = somealignment for x in something and not found: for y in somethingelse and not found: for z in evenmoresomething: if x+y+z highscore: highscore = x+y+z alignment = newalignment found = True break HTH, That's going to exit first time through, isn't it? -- Michael This mail was sent via Mail-SeCure System. This footnote confirms that this email message has been scanned by PineApp Mail-SeCure for the presence of malicious code, vandals computer viruses. ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] nested loops
Alan Gauld wrote: Wayne Werner waynejwer...@gmail.com wrote You probably want to add a sentinel to break out of the outer loops too: I don't think you want to break out of *any* of the loops. Otherwise you will skip testing combinations. In your example, the first time you set highscore and alignment, you break out of all three loops and only test the first triple x,y,z. found = False highscore = 0 alignment = somealignment for x in something and not found: for y in somethingelse and not found: for z in evenmoresomething: if x+y+z highscore: highscore = x+y+z alignment = newalignment found = True break That's the equivalent of a return in the innermost loop. If you're looking for the *first* matching highscore, that's fine, but not if you want the biggest. -- Steven ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] nested loops
Steven D'Aprano st...@pearwood.info wrote I don't think you want to break out of *any* of the loops. Otherwise you will skip testing combinations. In that case I misread the OP. I thought he specifically wanted to avoid testing all the options and exit when he reached his target. In your example, the first time you set highscore and alignment, you break out of all three loops Yep, thats what I thought was being asked for. It seems I mistook the intent. reading too quickly I suspect. Alan G ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] for loops when there is only one row in the result - is there an alternative?
Im using the py-postgresql module (docs here: http://python.projects.postgresql.org/docs/1.0/) in a python 3.1 environment to connect to my database. so far everything is working, but I'm having trouble understanding the structure of the variable returned by a select statement Generally you have something like this: clientlist = get_clients() # where get_clients is a prepared sql statement. normally you would get the individual rows like this: for row in clientlist: do stuff which is great for a long list of results. But I'm running into issues when there are only 0 or 1 results in the set. if there are zero rows then I can do something like: if len(clientlist) == 0: do stuff I'm looking for a better way to access the row when there is just one row in the result. Say from a user login attempt, or a request to edit an existing client record. Is there a decent way to get direct access to the single row in the result set without having to go through the for loop for just one item? It likely helps to know exactly what variable type clientlist would be. I have no idea. What I can say is that once you do get the row result, you can refer to values in the row with syntax like row[columnname], but I'm honestly not sure if this is helpful information. Ive read the module docs looking for something interesting, but I can't seem to find this particular tidbit. If I have to do the for loop fine, but I just thought it looked a little ugly. Rance ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] for loops when there is only one row in the result - is there an alternative?
Rance Hall wrote: Generally you have something like this: clientlist = get_clients() # where get_clients is a prepared sql statement. normally you would get the individual rows like this: for row in clientlist: do stuff which is great for a long list of results. But I'm running into issues when there are only 0 or 1 results in the set. If clientlist is empty, you don't need to explicitly test for it: clientlist = [] # nothing there for row in clientlist: ... print(Hello world) ... Notice that nothing gets printed. if there are zero rows then I can do something like: if len(clientlist) == 0: do stuff Generally one merely needs to check the list itself: if clientlist: ... although be warned that lazy lists, or iterators, are slightly different -- but if len(clientlist) works, then this should also work. I'm looking for a better way to access the row when there is just one row in the result. This should work: row, = clientlist # if one row only -- note the comma! row1, row2 = clientlist # if two rows row1, row2, row3 = clientlist # three rows If the comma in the first example is too subtle, try this: [row] = clientlist Another way which should work: row = clientlist[0] Say from a user login attempt, or a request to edit an existing client record. Is there a decent way to get direct access to the single row in the result set without having to go through the for loop for just one item? It likely helps to know exactly what variable type clientlist would be. I have no idea. type(clientlist) will tell you. -- Steven ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] While Loops: Coin Flip Game :p:
Hi there, This is the Code. Please check it.It is working fine. import random headsCount = 0 tailsCount = 0 count = 1 while count = 100: coin = random.randrange(2) if coin == 0: headsCount += 1 else: tailsCount += 1 count += 1 print The number of heads was, headsCount print The number of tails was, tailsCount raw_input(\n\nPress the enter key to exit.) * Your Description *: On Tue, Nov 16, 2010 at 1:25 PM, Dave Angel da...@ieee.org wrote: When I run this code (I'm also a noob) I get this result:- [evaluate lines 1-22 from untitled-1.py] The number of heads was 73 The number of tails was 100 Press the enter key to exit. # Surely, if flipping a single coin 100 times your total number of heads and tails should add up to 100 # not 173 or am I missing the point? No, you're missing an indentation. If you check the code you're running, I think you'll find that you didn't unindent the line incrementing count. Of course, it's less error prone to simply use for count in xrange(100): instead of while count 100: and you wouldn't need to increment count. DaveA -- With Regards, Nithya S ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] While Loops: Coin Flip Game :p:
Thankyou..!!! Regards, Nithya On Tue, Nov 16, 2010 at 1:51 PM, Luke Pettit petl...@gmail.com wrote: Arrr thats better Nithya it works fine now. I had it working fine before it was just coming up with that strange result of 73 and 100 when I copied the code into wing to check it out in order to understand it. Wing picked up the spacing and I had already corrected that Dave as I was simply looking at Nithya code. On 16 November 2010 19:10, Nithya Nisha nithyakarpa...@gmail.com wrote: Hi there, This is the Code. Please check it.It is working fine. import random headsCount = 0 tailsCount = 0 count = 1 while count = 100: coin = random.randrange(2) if coin == 0: headsCount += 1 else: tailsCount += 1 count += 1 print The number of heads was, headsCount print The number of tails was, tailsCount raw_input(\n\nPress the enter key to exit.) * Your Description *: On Tue, Nov 16, 2010 at 1:25 PM, Dave Angel da...@ieee.org wrote: When I run this code (I'm also a noob) I get this result:- [evaluate lines 1-22 from untitled-1.py] The number of heads was 73 The number of tails was 100 Press the enter key to exit. # Surely, if flipping a single coin 100 times your total number of heads and tails should add up to 100 # not 173 or am I missing the point? No, you're missing an indentation. If you check the code you're running, I think you'll find that you didn't unindent the line incrementing count. Of course, it's less error prone to simply use for count in xrange(100): instead of while count 100: and you wouldn't need to increment count. DaveA -- With Regards, Nithya S -- Luke Pettit ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] While Loops: Coin Flip Game :p:
Greetings, As a thread starter, I thought I should write the rewritten code I got that others helped me get to, since this thread is still going on. # Coin Flips# The program flips a coin 100 times and then# tells you the number of heads and tailsimport random print \aprint \tWelcome to 'Coin Flipper!'print \nI will flip a coin 100 times and then tell youprint the number of heads and tails!\n # set the coinheadsCount = 0tailsCount = 0count = 1 while count = 100:coin = random.randrange(2)if coin == 0: headsCount += 1else:tailsCount += 1count += 1 print The number of heads was, headsCountprint The number of tails was, tailsCount raw_input(\n\nPress the enter key to exit.) ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] While Loops: Coin Flip Game :p:
Stephanie Dawn Samson sd...@live.ca wrote thought I should write the rewritten code I got that others helped me get to By applying a couple of other ideas that have been suggested you get something shorter and arguably slightly clearer: # Coin Flips # The program flips a coin 100 times and then # tells you the number of heads and tails import random print Welcome to 'Coin Flipper!' I will flip a coin 100 times and then tell you the number of heads and tails! headsCount = 0 for count in range(100): if random.randrange(2): # returns 1/0 = true/False headsCount += 1 print The number of heads was, headsCount print The number of tails was, 100-headsCount raw_input(\n\nPress the enter key to exit.) And you could replace the whole for loop with a generator expression if you really wanted to, but I suspect that is getting into advanced territory for you at this stage... HTH, -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] While Loops: Coin Flip Game :p:
Just for the heck of it: heads = sum(random.randrange(2) for i in range(100)) -- Bob Gailer 919-636-4239 Chapel Hill NC ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] While Loops: Coin Flip Game :p:
Hi Tom, Your code is almost correct. Little mistake is there.The random number generate should be in while loop. import random # set the coin headsCount = 0 tailsCount = 0 count = 0 # the loop while count 100: #If you declare count = 0. The while loop condition should be less than 100.Else you will get 101 counts. *coin = random.randrange(2)* if coin == 0: headsCount += 1 else: #Becase We already declared randrange(2).So the coin value is 0 or 1.So we can use else condition. tailsCount += 1 count += 1 print The number of heads was, headsCount print The number of tails was, tailsCount raw_input(\n\nPress the enter key to exit.) Regards, Nithya _ * Your Description*: On Mon, Nov 15, 2010 at 7:19 AM, Thomas C. Hicks para...@pobox.com wrote: On Sun, 14 Nov 2010 17:16:36 -0500 Dawn Samson sd...@live.ca wrote: Greetings, I'm a Python beginner and working my way through Michael Dawson's Python Programming for the Absolute Beginner. I'm stuck in a particular challenge that asks me to write a program that flips a coin 100 times and then tells you the number of heads and tails. I've been trying to work on this challenge for a while now and can't get it to work (either it has 100 heads or 100 tails). I've been reworking this code many times and currently what I have does not do anything at all at IDLE. Please take a look at my code below: import random # set the coin coin = random.randrange(2) headsCount = 0 tailsCount = 0 count = 0 # the loop while count = 100: coin if coin == 0: headsCount += 1 if coin == 1: tailsCount += 1 count += 1 print The number of heads was, heads print The number of tails was, tails raw_input(\n\nPress the enter key to exit.) Thanks, S. Dawn Samson From one beginner to another - it looks to me like you set the value of coin once then checked it 100 times. If you want to reset the value of coin maybe it (i.e. setting the value of coin, not just calling the value of coin) should be in the loop too? tom ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] While Loops: Coin Flip Game :p:
When I run this code (I'm also a noob) I get this result:- [evaluate lines 1-22 from untitled-1.py] The number of heads was 73 The number of tails was 100 Press the enter key to exit. # Surely, if flipping a single coin 100 times your total number of heads and tails should add up to 100 # not 173 or am I missing the point? On 16 November 2010 15:08, Nithya Nisha nithyakarpa...@gmail.com wrote: Hi Tom, Your code is almost correct. Little mistake is there.The random number generate should be in while loop. import random # set the coin headsCount = 0 tailsCount = 0 count = 0 # the loop while count 100: #If you declare count = 0. The while loop condition should be less than 100.Else you will get 101 counts. *coin = random.randrange(2)* if coin == 0: headsCount += 1 else: #Becase We already declared randrange(2).So the coin value is 0 or 1.So we can use else condition. tailsCount += 1 count += 1 print The number of heads was, headsCount print The number of tails was, tailsCount raw_input(\n\nPress the enter key to exit.) Regards, Nithya _ * Your Description*: On Mon, Nov 15, 2010 at 7:19 AM, Thomas C. Hicks para...@pobox.comwrote: On Sun, 14 Nov 2010 17:16:36 -0500 Dawn Samson sd...@live.ca wrote: Greetings, I'm a Python beginner and working my way through Michael Dawson's Python Programming for the Absolute Beginner. I'm stuck in a particular challenge that asks me to write a program that flips a coin 100 times and then tells you the number of heads and tails. I've been trying to work on this challenge for a while now and can't get it to work (either it has 100 heads or 100 tails). I've been reworking this code many times and currently what I have does not do anything at all at IDLE. Please take a look at my code below: import random # set the coin coin = random.randrange(2) headsCount = 0 tailsCount = 0 count = 0 # the loop while count = 100: coin if coin == 0: headsCount += 1 if coin == 1: tailsCount += 1 count += 1 print The number of heads was, heads print The number of tails was, tails raw_input(\n\nPress the enter key to exit.) Thanks, S. Dawn Samson From one beginner to another - it looks to me like you set the value of coin once then checked it 100 times. If you want to reset the value of coin maybe it (i.e. setting the value of coin, not just calling the value of coin) should be in the loop too? tom ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor -- Luke Pettit ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] While Loops: Coin Flip Game :p:
Hi Tom, Your code is almost correct. Little mistake is there.The random number generate should be in while loop. import random # set the coin headsCount = 0 tailsCount = 0 count = 0 # the loop while count 100: #If you declare count = 0. The while loop condition should be less than 100.Else you will get 101 counts. *coin = random.randrange(2)* if coin == 0: headsCount += 1 else: #Becase We already declared randrange(2).So the coin value is 0 or 1.So we can use else condition. tailsCount += 1 count += 1 print The number of heads was, headsCount print The number of tails was, tailsCount raw_input(\n\nPress the enter key to exit.) Regards, Nithya __ *Your Description* On Mon, Nov 15, 2010 at 7:19 AM, Thomas C. Hicks para...@pobox.com wrote: On Sun, 14 Nov 2010 17:16:36 -0500 Dawn Samson sd...@live.ca wrote: Greetings, I'm a Python beginner and working my way through Michael Dawson's Python Programming for the Absolute Beginner. I'm stuck in a particular challenge that asks me to write a program that flips a coin 100 times and then tells you the number of heads and tails. I've been trying to work on this challenge for a while now and can't get it to work (either it has 100 heads or 100 tails). I've been reworking this code many times and currently what I have does not do anything at all at IDLE. Please take a look at my code below: import random # set the coin coin = random.randrange(2) headsCount = 0 tailsCount = 0 count = 0 # the loop while count = 100: coin if coin == 0: headsCount += 1 if coin == 1: tailsCount += 1 count += 1 print The number of heads was, heads print The number of tails was, tails raw_input(\n\nPress the enter key to exit.) Thanks, S. Dawn Samson From one beginner to another - it looks to me like you set the value of coin once then checked it 100 times. If you want to reset the value of coin maybe it (i.e. setting the value of coin, not just calling the value of coin) should be in the loop too? tom ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor -- With Regards, Nithya S ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] While Loops: Coin Flip Game :p:
When I run this code (I'm also a noob) I get this result:- [evaluate lines 1-22 from untitled-1.py] The number of heads was 73 The number of tails was 100 Press the enter key to exit. # Surely, if flipping a single coin 100 times your total number of heads and tails should add up to 100 # not 173 or am I missing the point? No, you're missing an indentation. If you check the code you're running, I think you'll find that you didn't unindent the line incrementing count. Of course, it's less error prone to simply use for count in xrange(100): instead of while count 100: and you wouldn't need to increment count. DaveA ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] While Loops: Coin Flip Game
On Sun, Nov 14, 2010 at 11:16 PM, Dawn Samson sd...@live.ca wrote: Greetings, I'm a Python beginner and working my way through Michael Dawson's Python Programming for the Absolute Beginner. I'm stuck in a particular challenge that asks me to write a program that flips a coin 100 times and then tells you the number of heads and tails. I've been trying to work on this challenge for a while now and can't get it to work (either it has 100 heads or 100 tails). I've been reworking this code many times and currently what I have does not do anything at all at IDLE. Please take a look at my code below: When you, as you say it, set the coin, you call the randrange function. This picks a random number between 0 and 1 and returns it. You then assign that number to the coin variable. So at this point, coin contains either 0 or 1. In the while loop, you have a line that simply says coin. You probably think that this calls the function again, but it doesn't. What it actually does is nothing. You simply mention the variable to the interpreter, which retrieves its value (0 or 1). Since you don't do anything with that value, it is simply immediately discarded again. You need to change your code so that the coin isn't set only once, but every iteration of the loop. Hope that helps Hugo ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] While Loops: Coin Flip Game
Dawn Samson wrote: I've been trying to work on this challenge for a while now and can't get it to work (either it has 100 heads or 100 tails). Unfortunately your code has been mangled in the email, but I can guess your problem: you need to set coin = random.randrange(2) each time through the loop, not just once outside the loop. -- Steven ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] While Loops: Coin Flip Game
Thanks everyone! I should be using algorithms for even such programs at my level. The solution to reiterate the coin flip every time in the loop works. Thanks a lot! Dawn ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] While Loops: Coin Flip Game
On 14/11/10 22:16, Dawn Samson wrote: Greetings, I'm a Python beginner and working my way through Michael Dawson's Python Programming for the Absolute Beginner. I'm stuck in a particular challenge that asks me to write a program that flips a coin 100 times and then tells you the number of heads and tails. I've been trying to work on this challenge for a while now and can't get it to work (either it has 100 heads or 100 tails). I've been reworking this code many times and currently what I have does not do anything at all at IDLE. Please take a look at my code below: import random # set the coin coin = random.randrange(2) headsCount = 0 tailsCount = 0 count = 0 # the loop while count = 100: coin if coin == 0: headsCount += 1 if coin == 1: tailsCount += 1 count += 1 print The number of heads was, heads print The number of tails was, tails raw_input(\n\nPress the enter key to exit.) Thanks, S. Dawn Samson You try to print two variables, heads and tails which don't exist. The other replies covered the other main problems. ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] While Loops: Coin Flip Game
From: tutor-bounces+bermanrl=cfl.rr@python.org [mailto:tutor-bounces+bermanrl=cfl.rr@python.org] On Behalf Of Dawn Samson Sent: Sunday, November 14, 2010 5:17 PM To: tutor@python.org Subject: [Tutor] While Loops: Coin Flip Game Greetings, I'm a Python beginner and working my way through Michael Dawson's Python Programming for the Absolute Beginner import random # set the coin coin = random.randrange(2) headsCount = 0 tailsCount = 0 count = 0 # the loop while count = 100: coin if coin == 0: headsCount += 1 if coin == 1: tailsCount += 1 count += 1 print The number of heads was, heads print The number of tails was, tails raw_input(\n\nPress the enter key to exit.) Thanks, S. Dawn Samson Hi, Think in terms of logical steps. You need to generate the results of a random coin toss for every toss of the coin. Therefore, if you are tossing 100 tosses, you need to generate 100 results based on a probability of zero or one. Since this is your homework assignment you write the code, but in terms of a logical frame work you would have something like the following. Tossknt = 1 Generate a random toss ; results being either one or 0. Further , assume 0 is tail; heads is one. If toss = 1 headcount = headcount + 1 Else tailcount = tailcount + 1 Tossknt = Tossknt + 1 If Tossknt 100 Continue loop Else print nbr of heads tossed = , headcount Print nbr of tails tossed = , tailcount Obviously, this is not valid python code but it should give you enough information to solve your problem. Good luck, Robert -- I am using the free version of SPAMfighter. We are a community of 7 million users fighting spam. SPAMfighter has removed 53 of my spam emails to date. Get the free SPAMfighter here: http://www.spamfighter.com/len The Professional version does not have this message ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] While Loops: Coin Flip Game :p:
On Sun, 14 Nov 2010 17:16:36 -0500 Dawn Samson sd...@live.ca wrote: Greetings, I'm a Python beginner and working my way through Michael Dawson's Python Programming for the Absolute Beginner. I'm stuck in a particular challenge that asks me to write a program that flips a coin 100 times and then tells you the number of heads and tails. I've been trying to work on this challenge for a while now and can't get it to work (either it has 100 heads or 100 tails). I've been reworking this code many times and currently what I have does not do anything at all at IDLE. Please take a look at my code below: import random # set the coin coin = random.randrange(2) headsCount = 0 tailsCount = 0 count = 0 # the loop while count = 100: coin if coin == 0: headsCount += 1 if coin == 1: tailsCount += 1 count += 1 print The number of heads was, heads print The number of tails was, tails raw_input(\n\nPress the enter key to exit.) Thanks, S. Dawn Samson From one beginner to another - it looks to me like you set the value of coin once then checked it 100 times. If you want to reset the value of coin maybe it (i.e. setting the value of coin, not just calling the value of coin) should be in the loop too? tom ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] while loops causing python.exe to crash on windows
Alex Hall mehg...@gmail.com wrote I am not sure how else to explain it. I want to loop until the value of a variable changes, but while that loop is taking place, the user should be able to perform actions set up in a wx.AcceleratorTable. And here we have the critical clue. You are trying to write this loop in a GUI application. GUIs and long running loops don't mix. GUIs are driven by events and if you write a long loop the GUI cannot receive any events until the loop finishes and so locks up In a GUI environment you simulate a long loop with 1) A Timer event that does someting then sets up another timer 2) The null event (if the framework suipports it) whereby when no other events are present the framework calls your code. for a listener, which will sit in the background and only perform an action when it detects a certain thing. In this case, a listener to watch for a variable to turn from False to True, then to act when it sees that change. The listener sits inside a Timer that fires every, say, 1/10 sec. That should leave plenty time to respond to the variable change and give wx time to process any mouse clicks, key presses etc. BTW. If you are doing any significant GUI work in wxPython it will be helpful to buy the wxPython in Action book. It is very clear and includes examples of using Timers etc. -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] while loops causing python.exe to crash on windows
On 7 June 2010 02:37, Alex Hall mehg...@gmail.com wrote: I am not sure how else to explain it. I want to loop until the value of a variable changes, but while that loop is taking place, the user should be able to perform actions set up in a wx.AcceleratorTable. Looping, though, causes Windows to tell me that python.exe is not responding, so I have to close the entire thing. I guess I am looking for a listener, which will sit in the background and only perform an action when it detects a certain thing. In this case, a listener to watch for a variable to turn from False to True, then to act when it sees that change. Notwithstanding what everyone else have said I'll add the following for what it's worth: You need to do some research into how GUI systems typically work, particularly the message queue and each applications magic and hidden message processing loop etc. Basically in a GUI app there's a hidden loop that continually checks for messages (calls) to your application and dispatches those calls to the handlers defined in your application. However, if your handlers do not complete quickly, then while they run, control obviously does not return to this loop again, and consequently no further events can/will be processed by your app. Some OS's flag up applications which do not process their event queues for a while as not responding or similar. However, in most windowing systems there's a way to process pending messages that have built up in the queue without actually returning from the handler that you're in. In Delphi the call is Application.ProcessMessages, in VB it's DoEvents. In WxPython it's Yield(). (You can google each of those to see the same issue in different languages/platforms if you like, it might be instructive.) So bottom line, in theory you can call Yield() in your loop and you should be OK -- your app should suddenly be responsive again even while in the loop. This type of solution is however the more cheap and dirty alternative and can introduce it's own set of problems and downsides. (What if for example another call/message is processed to the same event handler from which you called Yield() alrady? The point is you may open yourself up to re-entrancy issues if you're not careful. Also if the loop is very tight you might end-up consuming a lot of CPU doing nothing, so a sleep() type call might also be advisable in the loop to prevent spending more time calling Yield() than doing anything else. ) Anyway, I've done a quick google and the following page seems to be a good discussion of the above thoughts: http://wiki.wxpython.org/LongRunningTasks HTH, Walter ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] while loops causing python.exe to crash on windows
On 07/06/2010 01:44, Alex Hall wrote: Further to the other comments that you've had, could you please refer to the following, thanks. http://www.catb.org/~esr/faqs/smart-questions.html Kindest regards. Mark Lawrence ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] while loops / listeners
Hi all, I think that simply erasing those continue statements will let Python respond again. Those statements are both useless and damaging, because the following time.sleep(.1) statements will NEVER be executed. And this, in turn, is IMHO the reason why Python stops responding: it lacks the time to do so. Hope that helps Francesco Il 07/06/2010 5.09, Alex Hall wrote: Hi all, First off, I apologize to the list for my previous thread; somehow, despite my having written the post, it ended up blank () I have a main loop which will continue for as long as neither player1 nor player2 has won. Inside that loop I have a call to a function which should basically wait until the user completes a turn, then return, exiting this loop and returning to the main loop, the one looping until there is a winner. Once back there, the second player's idling function is called; once that user completes a turn, the main loop switches back to the first user, and so on. Here is the main loop: player1.takeTurn() #someone has to start off the game #now loop until someone wins... while not player1.isWinner and not player2.isWinner: if player1.grid.turnOver: #player1 is done for this turn player1.grid.speak(player 2 is going.) #lock p1 out of the window, unlock p2, and then loop p2 until s/he does something player1.lock(); player2.unlock(); player2.takeTurn() else: #player2 has completed a turn player2.grid.speak(player 1 is going.) #opposite of above - lock p2, unlock p1, loop until p1 is done player2.lock(); player1.unlock(); player1.takeTurn() #end if continue #is this doing anything? time.sleep(.1) #again, is this important? #end while The lock and unlock functions are simply there to disable and enable keyboard/mouse commands, respectively, so lock causes the player's screen to stop responding to input while unlock unfreezes the screen. This way, if you and I are playing a game, I can't keep shooting even if my turn is over. TakeTurn() is that smaller loop I was talking about: def takeTurn(self): while not self.grid.turnOver: #turnOver is true once a turn-ending function is called in grid continue time.sleep(.1) #end while #end def That is inside the Player class. Grid is just another object that is really the most important part of all the game logic; Grid holds the wx frame on which everything is drawn, the boolean to tell if the turn is over, the ships, and more. That is why the function checks self.grid.turnOver, instead of just self.turnOver; turnOver tells if the player has performed a move that ends a turn or not. Firing ends a turn, while just moving around does not. The question, then, is this: when I run the code, Windows says python.exe has stopped responding. I know that this is because it is getting stuck, probably in the takeTurn() loop. Ordinarily, a situation like this would probably call for: while ok: ok=#program logic The hard part with my program, though, is that all input is set up with a wx.AcceleratorTable object, so I cannot just dump everything into a huge while loop and have it process that way. What I am looking for is some kind of listener object, so that I can just monitor self.grid.turnOver and call a function, or perform a few lines of code, when the listener detects a change in turnOver. On the other hand, there may be something simple that I am missing in my while loop that would cause the problem of python.exe crashing to not happen (well, not crashing, but rather not responding). I hope it is the latter problem, but I am not sure what else I could add to the loop(s) to stop this problem. Thanks, and sorry again for the blank message; still not sure how that happened. Hopefully this one works! Nessun virus nel messaggio in arrivo. Controllato da AVG - www.avg.com Versione: 9.0.829 / Database dei virus: 271.1.1/2921 - Data di rilascio: 06/06/10 08:25:00 ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] while loops causing python.exe to crash on windows
-- Have a great day, Alex (msg sent from GMail website) mehg...@gmail.com; http://www.facebook.com/mehgcap ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] while loops causing python.exe to crash on windows
On 6/6/2010 8:44 PM, Alex Hall wrote: -- Have a great day, Alex (msg sent from GMail website) mehg...@gmail.com;http://www.facebook.com/mehgcap What is your question? -- Bob Gailer 919-636-4239 Chapel Hill NC ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] while loops causing python.exe to crash on windows
On 6/6/10, bob gailer bgai...@gmail.com wrote: On 6/6/2010 8:44 PM, Alex Hall wrote: -- Have a great day, Alex (msg sent from GMail website) mehg...@gmail.com;http://www.facebook.com/mehgcap What is your question? -- Bob Gailer 919-636-4239 Chapel Hill NC Why would that code cause Windows to consider the process not responding, and how can I fix this so I can have a sort of listener in place, awaiting a change in the grid.turnOver variable inside Player.takeTurn() so that the main while loop can switch to the other player once the one player's turn is over? I thought while loops would do it, but Windows sees them as making python.exe unresponsive. -- Have a great day, Alex (msg sent from GMail website) mehg...@gmail.com; http://www.facebook.com/mehgcap ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] while loops causing python.exe to crash on windows
On 06/07/10 11:08, Alex Hall wrote: On 6/6/10, bob gailer bgai...@gmail.com wrote: On 6/6/2010 8:44 PM, Alex Hall wrote: -- Have a great day, Alex (msg sent from GMail website) mehg...@gmail.com;http://www.facebook.com/mehgcap What is your question? -- Bob Gailer 919-636-4239 Chapel Hill NC Why would that code cause Windows to consider the process not responding, and how can I fix this so I can have a sort of listener in place, awaiting a change in the grid.turnOver variable inside Player.takeTurn() so that the main while loop can switch to the other player once the one player's turn is over? I thought while loops would do it, but Windows sees them as making python.exe unresponsive. Would you buy me a crystal ball to foresee what you're talking about? ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] while loops causing python.exe to crash on windows
On 6/6/10, Lie Ryan lie.1...@gmail.com wrote: On 06/07/10 11:08, Alex Hall wrote: On 6/6/10, bob gailer bgai...@gmail.com wrote: On 6/6/2010 8:44 PM, Alex Hall wrote: -- Have a great day, Alex (msg sent from GMail website) mehg...@gmail.com;http://www.facebook.com/mehgcap What is your question? -- Bob Gailer 919-636-4239 Chapel Hill NC Why would that code cause Windows to consider the process not responding, and how can I fix this so I can have a sort of listener in place, awaiting a change in the grid.turnOver variable inside Player.takeTurn() so that the main while loop can switch to the other player once the one player's turn is over? I thought while loops would do it, but Windows sees them as making python.exe unresponsive. Would you buy me a crystal ball to foresee what you're talking about? I am not sure how else to explain it. I want to loop until the value of a variable changes, but while that loop is taking place, the user should be able to perform actions set up in a wx.AcceleratorTable. Looping, though, causes Windows to tell me that python.exe is not responding, so I have to close the entire thing. I guess I am looking for a listener, which will sit in the background and only perform an action when it detects a certain thing. In this case, a listener to watch for a variable to turn from False to True, then to act when it sees that change. ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor -- Have a great day, Alex (msg sent from GMail website) mehg...@gmail.com; http://www.facebook.com/mehgcap ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] while loops causing python.exe to crash on windows
On 6/6/2010 9:37 PM, Alex Hall wrote: On 6/6/10, Lie Ryanlie.1...@gmail.com wrote: On 06/07/10 11:08, Alex Hall wrote: On 6/6/10, bob gailerbgai...@gmail.com wrote: On 6/6/2010 8:44 PM, Alex Hall wrote: -- Have a great day, Alex (msg sent from GMail website) mehg...@gmail.com;http://www.facebook.com/mehgcap What is your question? -- Bob Gailer 919-636-4239 Chapel Hill NC Why would that code What code. I don't see any! cause Windows to consider the process not responding, and how can I fix this so I can have a sort of listener in place, awaiting a change in the grid.turnOver variable inside Player.takeTurn() so that the main while loop can switch to the other player once the one player's turn is over? I thought while loops would do it, but Windows sees them as making python.exe unresponsive. Would you buy me a crystal ball to foresee what you're talking about? I am not sure how else to explain it. I want to loop until the value of a variable changes, but while that loop is taking place, the user should be able to perform actions set up in a wx.AcceleratorTable. Looping, though, causes Windows to tell me that python.exe is not responding, so I have to close the entire thing. I guess I am looking for a listener, which will sit in the background and only perform an action when it detects a certain thing. In this case, a listener to watch for a variable to turn from False to True, then to act when it sees that change. We are complaining because you first send a post with no content, then one with a question but no code. -- Bob Gailer 919-636-4239 Chapel Hill NC ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] while loops / listeners
Hi all, First off, I apologize to the list for my previous thread; somehow, despite my having written the post, it ended up blank () I have a main loop which will continue for as long as neither player1 nor player2 has won. Inside that loop I have a call to a function which should basically wait until the user completes a turn, then return, exiting this loop and returning to the main loop, the one looping until there is a winner. Once back there, the second player's idling function is called; once that user completes a turn, the main loop switches back to the first user, and so on. Here is the main loop: player1.takeTurn() #someone has to start off the game #now loop until someone wins... while not player1.isWinner and not player2.isWinner: if player1.grid.turnOver: #player1 is done for this turn player1.grid.speak(player 2 is going.) #lock p1 out of the window, unlock p2, and then loop p2 until s/he does something player1.lock(); player2.unlock(); player2.takeTurn() else: #player2 has completed a turn player2.grid.speak(player 1 is going.) #opposite of above - lock p2, unlock p1, loop until p1 is done player2.lock(); player1.unlock(); player1.takeTurn() #end if continue #is this doing anything? time.sleep(.1) #again, is this important? #end while The lock and unlock functions are simply there to disable and enable keyboard/mouse commands, respectively, so lock causes the player's screen to stop responding to input while unlock unfreezes the screen. This way, if you and I are playing a game, I can't keep shooting even if my turn is over. TakeTurn() is that smaller loop I was talking about: def takeTurn(self): while not self.grid.turnOver: #turnOver is true once a turn-ending function is called in grid continue time.sleep(.1) #end while #end def That is inside the Player class. Grid is just another object that is really the most important part of all the game logic; Grid holds the wx frame on which everything is drawn, the boolean to tell if the turn is over, the ships, and more. That is why the function checks self.grid.turnOver, instead of just self.turnOver; turnOver tells if the player has performed a move that ends a turn or not. Firing ends a turn, while just moving around does not. The question, then, is this: when I run the code, Windows says python.exe has stopped responding. I know that this is because it is getting stuck, probably in the takeTurn() loop. Ordinarily, a situation like this would probably call for: while ok: ok=#program logic The hard part with my program, though, is that all input is set up with a wx.AcceleratorTable object, so I cannot just dump everything into a huge while loop and have it process that way. What I am looking for is some kind of listener object, so that I can just monitor self.grid.turnOver and call a function, or perform a few lines of code, when the listener detects a change in turnOver. On the other hand, there may be something simple that I am missing in my while loop that would cause the problem of python.exe crashing to not happen (well, not crashing, but rather not responding). I hope it is the latter problem, but I am not sure what else I could add to the loop(s) to stop this problem. Thanks, and sorry again for the blank message; still not sure how that happened. Hopefully this one works! -- Have a great day, Alex (msg sent from GMail website) mehg...@gmail.com; http://www.facebook.com/mehgcap ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] Fw: loops
- Forwarded Message From: Richard Hultgren hultgren1...@yahoo.com To: tutor@python.org Sent: Mon, December 7, 2009 2:53:40 PM Subject: loops I'm quite new but determined. Can you explain to me, step by step, what is going on in the computer in this loop. I hope I am not being too dumb! a = 0 b = 1 count = 0 max_count = 20 while count max_count: count = count + 1 # we need to keep track of a since we change it old_a = a# especially here old_b = b a = old_b b = old_a + old_b # Notice that the , at the end of a print statement keeps it # from switching to a new line print old_a, ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Fw: loops
- Forwarded Message From: Richard Hultgren hultgren1...@yahoo.com To: tutor@python.org Sent: Mon, December 7, 2009 2:53:40 PM Subject: loops I'm quite new but determined. Can you explain to me, step by step, what is going on in the computer in this loop. I hope I am not being too dumb! Hmm...that still seems like quite a broad question. Can you be more specific about which portion you find confusing or unclear? If not, you might do better by starting with a general programming text. The top one is a list of texts for beginning programmers, followed by a few specific links to online texts: http://wiki.python.org/moin/BeginnersGuide/NonProgrammers http://www.freenetpages.co.uk/hp/alan.gauld/ http://swaroopch.com/notes/Python HTH, Serdar ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Fw: loops
You should probably read some of the links sent to you earlier but here is a stab at an explanation. Richard Hultgren wrote on 12/08/2009 10:36:08 AM: - Forwarded Message From: Richard Hultgren hultgren1...@yahoo.com To: tutor@python.org Sent: Mon, December 7, 2009 2:53:40 PM Subject: loops I'm quite new but determined. Can you explain to me, step by step, what is going on in the computer in this loop. I hope I am not being too dumb! a = 0 b = 1 count = 0 max_count = 20 The above steps are initialization of your variables. 'a' points to the value 0, 'b' points to 1, etc. Since the values of the variables are used within the loop we need to give it somewhere to start, otherwise we will get an error. while count max_count: The while loop will continue until 'count max_count' evaluates to False (20 loops, due to line below) the loop is defined as everything that is indented below this line. count = count + 1 Increase the value of count by one each loop iteration, otherwise the statement 'count max_count' will never change value, and the loop will never end. # we need to keep track of a since we change it old_a = a# especially here old_b = b Keep the old values of the variables since we want to add them together for the new value of b and will change the values in the next steps. a = old_b b = old_a + old_b reassign 'a' to the value of 'old_b'. If we didn't save the value of 'a' into 'old_a' above we wouldn't know what it was anymore. reassign 'b' to the sum of 'old_a' and 'old_b' # Notice that the , at the end of a print statement keeps it # from switching to a new line print old_a, prints the value of old_a followed by a space. Without the comma at the end the print statement each loop would print on a new line. The best way to follow what is happening is to trace the variables through the program. you would get a table that loops something like : max_count count a b old_a old_b countmax_count OUTPUT 20 0 0 1 no ValueNo Value T No output yet 20 1 1 1 0 1 T 0 20 2 1 2 1 1 T 0 1 20 3 2 3 1 2 T 0 1 1 20 4 3 5 2 3 T 0 1 1 2 20 5 5 8 3 5 T 0 1 1 2 3 20 6 8 13 5 8 T 0 1 1 2 3 5 . . . 20 19 2584676541812584T 0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597 2584 4181 20 20 2584676541812584F 0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597 2584 4181 (You might want to check the last two rows, not guaranteeing the values are right) In the last row countmax_count is False the loop won't run and therefore nothing will change. Hope this helps some, but would recommend you try following some of the tutorials online for beginning programming to help explain some of the concepts, feel free to ask here whenever you get confused. Chris ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Fw: loops
Serdar Tumgoren zstumgo...@gmail.com wrote http://www.freenetpages.co.uk/hp/alan.gauld/ Note the new URL in my sig. Freenet are due to close this site soon. Its been locked for over a year. -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] 'for' loops
On Tue, 02 Dec 2008 01:17:41 +, Alan Gauld wrote:
while loops are used much less in Python than in other languages because
for loops are so powerful.
Actually, I think python's for-loop is so powerful that while loop could
be removed from the language and no power would be lost (although many
idioms are much better (and faster) written in while loop). This is
because python allows infinite-length iterable, you can emulate while
True loop with something like this:
eternity = __import__('itertools').count()
for ever in eternity:
print can't stp
# the code above is slightly obfuscated,
# I wouldn't normally write it like that
# ...
# [1]
while lops are generally used in cases where you don't know how many
times you need to loop or you want to loop 'forever'.
while True:
print 'Can't stop me now!'
will keep on looping until you close the program
c = 0
while c != -1:
c = int(raw_input('Enter a number(-1 to stop) '))
print c
will keep looping until the user enters -1
while that can be turned into something like this:
for ever in eternity:
c = int(raw_input('Enter a number(-1 to stop) '))
print c
OR
from itertools import repeat
from functools import partial
def ask():
def stop(): raise StopIteration
asker = partial(raw_input, 'Enter a number(-1 to stop) ')
for n in repeat(asker):
n = n()
yield n if n != '-1' else stop()
for c in ask():
print c
More info and a comparison with JabaScript and VBScript can be found in
my tutor in the looping topic.
[1] I cheated slightly, there is a while loop in the C code for itertools
[2] I'm not suggesting that while loop should go away, I'm illustrating
the power of the for(ce).
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[Tutor] 'for' loops
I recently asked a question about 'for' loops, expecting them to be similar to 'for-next' loops. I have looked at several on-line tutors but am still in the dark about what 'for' loops do. Does anyone have a plain English about the use of 'for' loops? Are 'while' loops the only way Python runs a sub-routine over over? ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] 'for' loops
On Mon, Dec 01, 2008 at 04:44:02PM -0800, WM. wrote:
I recently asked a question about 'for' loops, expecting them to be
similar to 'for-next' loops. I have looked at several on-line tutors but
am still in the dark about what 'for' loops do.
Does anyone have a plain English about the use of 'for' loops?
Are 'while' loops the only way Python runs a sub-routine over over?
No, both 'while' and 'for' loops are for running a block of code
(whether subroutine calls or whatever) over and over. The difference
between the two is that 'while' will continue repeating the block
for however many iterations it takes until the condition is satisfied
('while x is true, for some expression x'), a 'for' loop will run the
block of code a set number of times ('once for each element of some
set of values').
So if you want to execute 'print' for every line of a file, you
would do this:
for line in file:
print line
If you wanted to double a value until it exceeded 100, you would
use a while loop:
while x = 100:
x *= 2
If you just want something executed a specific number of times,
(like print hello 10 times), you can use a for loop:
for i in range(10):
print hello
This is, just like any 'for' loop, executing the block once per
element of a list. The list in this case is range(10) which is
an expression that generates the list (0, 1, 2, ..., 9), so you
get one run through the code for each of those.
Does that help?
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Re: [Tutor] 'for' loops
On Mon, Dec 1, 2008 at 6:44 PM, WM. [EMAIL PROTECTED] wrote:
I recently asked a question about 'for' loops, expecting them to be similar
to 'for-next' loops. I have looked at several on-line tutors but am still
in the dark about what 'for' loops do.
Does anyone have a plain English about the use of 'for' loops?
Are 'while' loops the only way Python runs a sub-routine over over?
For loops are mainly used when you want a specific number of iterations,
such as looping over the elements of a list. In C/C++ you would do something
like this:
int myarray[] = {1, 2, 3, 4, 5};
for(int x = 0; x 5; x++)
printf(%d, myarray[x])
In python it would be much cleaner:
myarray = [1, 2, 3, 4, 5]
for x in myarray:
print x
HTH,
Wayne
--
To be considered stupid and to be told so is more painful than being called
gluttonous, mendacious, violent, lascivious, lazy, cowardly: every weakness,
every vice, has found its defenders, its rhetoric, its ennoblement and
exaltation, but stupidity hasn't. - Primo Levi
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Re: [Tutor] 'for' loops
On 02/12/2008, WM. [EMAIL PROTECTED] wrote: I recently asked a question about 'for' loops, expecting them to be similar to 'for-next' loops. I have looked at several on-line tutors but am still in the dark about what 'for' loops do. Does anyone have a plain English about the use of 'for' loops? Are 'while' loops the only way Python runs a sub-routine over over? I'm not sure exactly what you understand by a for-next loop. A for loop, essentially, iterates over a list [1]. e.g. for fruit in ['apple', 'pear', 'banana', 'tomato']: print fruit The loop will set the variable 'fruit' to be 'apple', 'pear', etc. on each pass through the loop. If you just want to do something n times, the usual idiom is: for i in range(n): # do something, possibly involving i range(n) is a function that will produce the list [0, 1, 2, ..., n-1]. Tutorials should cover this, so I'm not sure if I'm telling you anything new. If there's something particular you're stuck on, ask :-) -- John. [1] Technically, it iterates over an iterator, which you can think of as an object that behaves like a list when you throw it at a for loop. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] 'for' loops
WM. [EMAIL PROTECTED] wrote
I recently asked a question about 'for' loops, expecting them to be
similar to 'for-next' loops. I have looked at several on-line tutors
but am still in the dark about what 'for' loops do.
Python for loops are like foreach loops in other languages.
A Python for loop executes a bit of code for each element
in a sequence (list, string, dictionary, set, file etc)
It will keep looping until it runs out of items in the
sequence.
Thus to print each letter in a string:
mystring = 'foobar'
for ch in mystring:
print ch
Or to print each element of a list:
mlist = [1,'2,'a',45, True]
for item in mylist:
print item
And if you want to loop for a fixed number of iterations simply
construct
a list with that number of elements. The range() function does that
for
us, thus:
for n in range(12):
print 'hi'
will print 'hi' 12 times.
Does anyone have a plain English about the use of 'for' loops?
Are 'while' loops the only way Python runs a sub-routine over
over?
while loops are used much less in Python than in other languages
because for loops are so powerful.
while lops are generally used in cases where you don't know how
many times you need to loop or you want to loop 'forever'.
while True:
print 'Can't stop me now!'
will keep on looping until you close the program
c = 0
while c != -1:
c = int(raw_input('Enter a number(-1 to stop) '))
print c
will keep looping until the user enters -1
More info and a comparison with JabaScript and VBScript can be
found in my tutor in the looping topic.
--
Alan Gauld
Author of the Learn to Program web site
http://www.freenetpages.co.uk/hp/alan.gauld
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Tutor maillist - Tutor@python.org
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Re: [Tutor] 'for' loops
On Mon, Dec 1, 2008 at 7:56 PM, John Fouhy [EMAIL PROTECTED] wrote: [1] Technically, it iterates over an iterator, which you can think of as an object that behaves like a list when you throw it at a for loop. The object of the 'in' must be an iterable, which is an object that can produce an iterator when asked. A list is an iterable, not an iterator. Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] __iter__ loops, partitioning list among children
I finally got my iterator-based version working, only to discover that it's nearly four times slower than the brute-force multiple-loops version I started with! Then I tried just adding an incrementing index to the loop, so that each loop only ran through self.events[last_index:], but that was still twice as slow as without the index. I suppose it's the overhead of incrementing the variable, or maybe some optimization in Python's internals, but the take home lesson was definitely 'leave well enough alone'. Anyway, thanks again for the advice, it's been a learning experience... E On Aug 27, 2008, at 2:22 AM, Kent Johnson wrote: On Tue, Aug 26, 2008 at 1:24 PM, Eric Abrahamsen [EMAIL PROTECTED] wrote: On Aug 26, 2008, at 7:20 PM, Kent Johnson wrote: If all you want to do with the nested Month, etc is to iterate the events in them, you could probably use a shared iterator. It would have to be able to push-back items so that when you hit the out-of-range item you could push it back on the iterator. Is a 'shared iterator' something special, or do you mean all the instances would draw their events from a single iterator? I'm not sure what this would look like. It's nothing special, I just mean that all instances would share an iterator. You would pass the iterator to the iteration function. Just for the sake of argument, here's the principle I'm working from: # lst = range(10) iterlst = iter(lst) iterlst.next() 0 for x in iterlst: ... if x 5: ... print x ... else: ... break ... 1 2 3 4 for x in iterlst: ... print x ... 6 7 8 9 # So that's why I'm creating the iterator outside of the while loop in the original code, and then using a repeated for loop with a break to step through all the events only once. Of course, the fact that 5 isn't in there probably points to the source of my problems! The solution might be assigning iterlist.next() to a variable, and advancing the variable. The problem is that the first loop consumes the 5 from the iterator but doesn't actually process it. That is why you need an iterator with push-back - so you can put the 5 back in the iterator and get it out again in the next loop. http://code.activestate.com/recipes/502304/ Though working with indices directly might be simpler. Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] __iter__ loops, partitioning list among children
Just for the sake of argument, here's the principle I'm working from: # lst = range(10) iterlst = iter(lst) iterlst.next() 0 for x in iterlst: ... if x 5: ... print x ... else: ... break ... 1 2 3 4 for x in iterlst: ... print x ... 6 7 8 9 # If that contrived case is the case, you could change the code a bit to make 5 appears: for x in iterlst: print x if x = 5: break for x in iterlst: print x So that's why I'm creating the iterator outside of the while loop in the original code, and then using a repeated for loop with a break to step through all the events only once. Of course, the fact that 5 isn't in there probably points to the source of my problems! The solution might be assigning iterlist.next() to a variable, and advancing the variable. The problem is that the first loop consumes the 5 from the iterator but doesn't actually process it. That is why you need an iterator with push-back - so you can put the 5 back in the iterator and get it out again in the next loop. http://code.activestate.com/recipes/502304/ Though working with indices directly might be simpler. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] __iter__ loops, partitioning list among children
On Tue, Aug 26, 2008 at 1:36 AM, Eric Abrahamsen [EMAIL PROTECTED] wrote: So my test case: a Month has a 'child' attribute pointing at Week, which has a 'child' attribute pointing at Day, so they all know what kind of child instances iteration should produce. With nested loops, a Month produces one Week, that Week produces seven Days, then the next Week is produced, it makes seven more Days, etc. That much is easy. If all you want to do with the nested Month, etc is to iterate the events in them, you could probably use a shared iterator. It would have to be able to push-back items so that when you hit the out-of-range item you could push it back on the iterator. Then there's self.events. My original code looped over all of self.events for each child produced. A Month loops over its events four times, a Week seven times. This was the straightforward implementation, but it seemed inefficient. (I also, as you point out, might have been wrong about the way django QuerySets work). My thought was that only one loop over self.events should be necessary, in theory, since they're sorted by date. Instead of direct use of the list iterator, you could pass the list and the starting index around. Then you don't have to keep finding your place. A for loop creates an iterator from a sequence and calls next() on it, and it creates an entirely new iterator each time you start a new for loop: I still don't understand your code but you may have another misconception. Calling iter() on an iterator returns the same iterator; it does not make a new iterator that holds the same place. You can use itertools.tee() to split an iterator if that is what you want to do. Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] __iter__ loops, partitioning list among children
On Aug 26, 2008, at 7:20 PM, Kent Johnson wrote: On Tue, Aug 26, 2008 at 1:36 AM, Eric Abrahamsen [EMAIL PROTECTED] wrote: So my test case: a Month has a 'child' attribute pointing at Week, which has a 'child' attribute pointing at Day, so they all know what kind of child instances iteration should produce. With nested loops, a Month produces one Week, that Week produces seven Days, then the next Week is produced, it makes seven more Days, etc. That much is easy. If all you want to do with the nested Month, etc is to iterate the events in them, you could probably use a shared iterator. It would have to be able to push-back items so that when you hit the out-of-range item you could push it back on the iterator. Is a 'shared iterator' something special, or do you mean all the instances would draw their events from a single iterator? I'm not sure what this would look like. Then there's self.events. My original code looped over all of self.events for each child produced. A Month loops over its events four times, a Week seven times. This was the straightforward implementation, but it seemed inefficient. (I also, as you point out, might have been wrong about the way django QuerySets work). My thought was that only one loop over self.events should be necessary, in theory, since they're sorted by date. Instead of direct use of the list iterator, you could pass the list and the starting index around. Then you don't have to keep finding your place. That's a definite possibility, I'll try it out. Itertools.tee is also something I've yet to look at closely. Thanks for these hints. A for loop creates an iterator from a sequence and calls next() on it, and it creates an entirely new iterator each time you start a new for loop: I still don't understand your code but you may have another misconception. Calling iter() on an iterator returns the same iterator; it does not make a new iterator that holds the same place. You can use itertools.tee() to split an iterator if that is what you want to do. Just for the sake of argument, here's the principle I'm working from: # lst = range(10) iterlst = iter(lst) iterlst.next() 0 for x in iterlst: ... if x 5: ... print x ... else: ... break ... 1 2 3 4 for x in iterlst: ... print x ... 6 7 8 9 # So that's why I'm creating the iterator outside of the while loop in the original code, and then using a repeated for loop with a break to step through all the events only once. Of course, the fact that 5 isn't in there probably points to the source of my problems! The solution might be assigning iterlist.next() to a variable, and advancing the variable. Thanks, Eric ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] __iter__ loops, partitioning list among children
Eric Abrahamsen [EMAIL PROTECTED] wrote So that's why I'm creating the iterator outside of the while loop in the original code, and then using a repeated for loop with a break to step through all the events only once. Of course, the fact that 5 isn't in there probably points to the source of my problems! The solution might be assigning iterlist.next() to a variable, and advancing the variable. In that case wouldn't it be simpler to just use the index and manually control its value? Iterators are wonderful things but when I have to start bending things too far from vanilla I tend to go back to first principles. -- Alan Gauld Author of the Learn to Program web site http://www.freenetpages.co.uk/hp/alan.gauld ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] __iter__ loops, partitioning list among children
On Tue, Aug 26, 2008 at 1:24 PM, Eric Abrahamsen [EMAIL PROTECTED] wrote: On Aug 26, 2008, at 7:20 PM, Kent Johnson wrote: If all you want to do with the nested Month, etc is to iterate the events in them, you could probably use a shared iterator. It would have to be able to push-back items so that when you hit the out-of-range item you could push it back on the iterator. Is a 'shared iterator' something special, or do you mean all the instances would draw their events from a single iterator? I'm not sure what this would look like. It's nothing special, I just mean that all instances would share an iterator. You would pass the iterator to the iteration function. Just for the sake of argument, here's the principle I'm working from: # lst = range(10) iterlst = iter(lst) iterlst.next() 0 for x in iterlst: ... if x 5: ... print x ... else: ... break ... 1 2 3 4 for x in iterlst: ... print x ... 6 7 8 9 # So that's why I'm creating the iterator outside of the while loop in the original code, and then using a repeated for loop with a break to step through all the events only once. Of course, the fact that 5 isn't in there probably points to the source of my problems! The solution might be assigning iterlist.next() to a variable, and advancing the variable. The problem is that the first loop consumes the 5 from the iterator but doesn't actually process it. That is why you need an iterator with push-back - so you can put the 5 back in the iterator and get it out again in the next loop. http://code.activestate.com/recipes/502304/ Though working with indices directly might be simpler. Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] __iter__ loops, partitioning list among children
Okay I think I'm onto something, more iterator-related stuff. If I can make self.events an iterator, then run a for loop on it, breaking out of the loop when the events' date attributes get too high. Then on the next run through, that same for loop should pick up where it left off, right? Here's my next version of the function. It doesn't quite work right: when I test it each child instance receives the correct events, but when it passes those events onto its children, they get consumed (or something) and are never actually output. To test I'm instantiating a Month m, filling it with events, then looping like so: for w in m: print w.event_count() for d in w: print d.events w.event_count() produces the right event count, but d.events is always empty. If anyone can see what's wrong with this function... ## def _iter_children(self, child, require_events=False): Iterate through an object's 'child' items. If require_events == True, only return children with events, otherwise return all children. iterevents = iter(self.events) while self.sentinel self.stop: c = child([], self.sentinel, self.start_attr, rolling=self.rolling, counts_only=self.counts_only) for e in iterevents: if getattr(e, self.start_attr) c.stop: c.events.append(e) else: break self.sentinel += c.dt_range if not require_events or c.has_events(): # if require_events == True, omit empty children. yield c On Aug 25, 2008, at 11:49 AM, Eric Abrahamsen wrote: On Aug 24, 2008, at 7:20 PM, Kent Johnson wrote: Forwarding to the list with my reply. Please use Reply All to reply to the list. Grr, sorry, I keep forgetting... On Sun, Aug 24, 2008 at 1:02 AM, Eric Abrahamsen [EMAIL PROTECTED] wrote: On Aug 23, 2008, at 11:22 PM, Kent Johnson wrote: On Sat, Aug 23, 2008 at 6:47 AM, Eric Abrahamsen [EMAIL PROTECTED] wrote: At first I thought the bisect module was the way to go, but it is too tightly tied to integer list indices, and works very awkwardly when bisecting on datetime attributes. I'm not sure what the problem is with bisect (to find the starting point). Your list of model elements has integer indices. I think you have to write a __cmp__ method for your model class that compares on the datetime attribute, then it should work. You can also create a list of (key, model) and sort/search that. http://www.mail-archive.com/[EMAIL PROTECTED]/msg189443.html The __cmp__ trick is very nice, and would do it, except I won't have access to the events model classes. I could get bisect to work by feeding it a list comprehension, but making the high and low parameters work required integer indices, which seemed like one half-hack too many... I don't understand the issue. *All* lists have integer indices. If you make a list of (key, model) pairs, the keys only need to be comparable, not integers. The main problem is that I don't have any control over the list of models, and all I've got is the name of a datetime attribute to filter by. The only way I could get bisect to work was like this: index = bisect([getattr(x, attr_name) for x in model_list], sentinel_date) But that loops over the whole list, which is what I was trying to avoid. And the only way I could provide high and low parameters to bisect is by calling event_list.index(event), which doesn't work on django querysets. I also experimented with itertools.groupby to produce groups of events, but that turned out to be far slower than simply looping over the whole event list and extracting events which test true for c.start = getattr(event, attr_name) c.stop. Ideally I could create a kind of concurrent iterator, that steps through children's blocks of time and the object's event list in tandem, rather than going over the whole events list once for every child produced. Maybe that's not possible... I'm pasting the whole function down below, just for the hell of it. Thanks again, Eric def _iter_children(self, child, require_events=False): Iterate through an object's 'child' items. If require_events == True, only return children with events, otherwise return all children. while self.sentinel self.stop: c = child([], self.sentinel, self.start_attr, rolling=self.rolling, counts_only=self.counts_only) for e in self.events: if c.start = getattr(e,self.start_attr) c.stop: c.events.append(e) self.sentinel += c.dt_range if not require_events or c.has_events(): yield c ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor ___ Tutor maillist - Tutor@python.org
Re: [Tutor] __iter__ loops, partitioning list among children
I'm not following your code very well. I don't understand the relationship between the first loop and the iter_children() function. A couple of things that might help: - Django QuerySets can be qualified with additional tests, so you could have each of your month/week/etc classes have its own correctly qualified QuerySet. This will result in one database query for each event class, and multiple copies of the actual events. - When you start iterating a QuerySet, it fetches all the model instances into a list. I think you are trying to use iterators to prevent this fetch but Django doesnt' work that way. You might as well just use the list. - Iterators can't be restarted, I think that is why your latest iter_children() doesn't work as you expect. Can you say some more about why you are doing this? Where do all the initial constraints come from? Do you really have to be so careful to protect against a 'madman' user? Perhaps you could set a limit on the number of events you will retrieve and use a count() on the QuerySet to ensure that not too many records have been fetched. Maybe you should try a straightforward implementation and when you have something working you can worry about making it better. Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] __iter__ loops, partitioning list among children
I do apologize for the large quantities of confusing description – articulating the problem here has helped me understand exactly what it is I'm after (though it hasn't improved my code!), and I've got a better grasp of the problem now than I did when I first asked. It isn't so much that I need to protect against crazy users, but that the pattern I'm making is very flexible, and could be used in vastly different ways. I want to make sure that it operates on efficient principles, so that people will get the best performance out of it no matter how they use it. So my test case: a Month has a 'child' attribute pointing at Week, which has a 'child' attribute pointing at Day, so they all know what kind of child instances iteration should produce. With nested loops, a Month produces one Week, that Week produces seven Days, then the next Week is produced, it makes seven more Days, etc. That much is easy. Then there's self.events. My original code looped over all of self.events for each child produced. A Month loops over its events four times, a Week seven times. This was the straightforward implementation, but it seemed inefficient. (I also, as you point out, might have been wrong about the way django QuerySets work). My thought was that only one loop over self.events should be necessary, in theory, since they're sorted by date. A for loop creates an iterator from a sequence and calls next() on it, and it creates an entirely new iterator each time you start a new for loop: each for loop starts from the beginning of the sequence. But if you create your own iterator from the sequence and run a for loop on it, then using break to jump out of the for loop should leave the iterator just where you left it, since it maintains state. Doing another for loop on it (the next time through the date-based while loop), should pick up where it left off. That's why the line iterevents = iter(self.events) is outside of the while loop: it is only created once, and the loops later in the function all make use of the same iterator, instead of creating a new one every time. I'm pretty sure this works in theory, because calling event_count() on the Weeks as they come out returns the correct number of events. But, for some reason, those events are not making it into the Day children. I had originally assumed that a QuerySet pulled objects out of the database in a rolling fashion – ie iterating on a Month would first draw a Week's worth of events from the database, then another Week, then two more. But if it loads them all at first access, then I might as well just call list() on the QuerySet at object instantiation, and save myself some trouble. I hope that's a little clearer. My central issue is maintaining my place in the self.events loop, and only advancing it as far as the date-based while loop advances. Whether that's possible or not... Thanks again, Eric On Aug 26, 2008, at 1:12 AM, Kent Johnson wrote: I'm not following your code very well. I don't understand the relationship between the first loop and the iter_children() function. A couple of things that might help: - Django QuerySets can be qualified with additional tests, so you could have each of your month/week/etc classes have its own correctly qualified QuerySet. This will result in one database query for each event class, and multiple copies of the actual events. - When you start iterating a QuerySet, it fetches all the model instances into a list. I think you are trying to use iterators to prevent this fetch but Django doesnt' work that way. You might as well just use the list. - Iterators can't be restarted, I think that is why your latest iter_children() doesn't work as you expect. Can you say some more about why you are doing this? Where do all the initial constraints come from? Do you really have to be so careful to protect against a 'madman' user? Perhaps you could set a limit on the number of events you will retrieve and use a count() on the QuerySet to ensure that not too many records have been fetched. Maybe you should try a straightforward implementation and when you have something working you can worry about making it better. Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] __iter__ loops, partitioning list among children
On Aug 24, 2008, at 7:20 PM, Kent Johnson wrote: Forwarding to the list with my reply. Please use Reply All to reply to the list. Grr, sorry, I keep forgetting... On Sun, Aug 24, 2008 at 1:02 AM, Eric Abrahamsen [EMAIL PROTECTED] wrote: On Aug 23, 2008, at 11:22 PM, Kent Johnson wrote: On Sat, Aug 23, 2008 at 6:47 AM, Eric Abrahamsen [EMAIL PROTECTED] wrote: At first I thought the bisect module was the way to go, but it is too tightly tied to integer list indices, and works very awkwardly when bisecting on datetime attributes. I'm not sure what the problem is with bisect (to find the starting point). Your list of model elements has integer indices. I think you have to write a __cmp__ method for your model class that compares on the datetime attribute, then it should work. You can also create a list of (key, model) and sort/search that. http://www.mail-archive.com/[EMAIL PROTECTED]/msg189443.html The __cmp__ trick is very nice, and would do it, except I won't have access to the events model classes. I could get bisect to work by feeding it a list comprehension, but making the high and low parameters work required integer indices, which seemed like one half-hack too many... I don't understand the issue. *All* lists have integer indices. If you make a list of (key, model) pairs, the keys only need to be comparable, not integers. The main problem is that I don't have any control over the list of models, and all I've got is the name of a datetime attribute to filter by. The only way I could get bisect to work was like this: index = bisect([getattr(x, attr_name) for x in model_list], sentinel_date) But that loops over the whole list, which is what I was trying to avoid. And the only way I could provide high and low parameters to bisect is by calling event_list.index(event), which doesn't work on django querysets. I also experimented with itertools.groupby to produce groups of events, but that turned out to be far slower than simply looping over the whole event list and extracting events which test true for c.start = getattr(event, attr_name) c.stop. Ideally I could create a kind of concurrent iterator, that steps through children's blocks of time and the object's event list in tandem, rather than going over the whole events list once for every child produced. Maybe that's not possible... I'm pasting the whole function down below, just for the hell of it. Thanks again, Eric def _iter_children(self, child, require_events=False): Iterate through an object's 'child' items. If require_events == True, only return children with events, otherwise return all children. while self.sentinel self.stop: c = child([], self.sentinel, self.start_attr, rolling=self.rolling, counts_only=self.counts_only) for e in self.events: if c.start = getattr(e,self.start_attr) c.stop: c.events.append(e) self.sentinel += c.dt_range if not require_events or c.has_events(): yield c ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] __iter__ loops, partitioning list among children
Hi, I've got a problem that takes a bit of explaining, but it's relatively simple when you get down to it. This is another django-related thing, but the issue itself is pure python. I made a custom class, called an EventEngine, which represents a span of time. You initialize it with a queryset/list of django model instances, and the resulting EventEngine object has an 'events' attribute, which is a queryset/list of model instances that fall within that span of time, according to a datetime attribute on the django model. Next come EventEngine subclasses, representing commonly used spans of time – Month, Week, Day, etc. The EventEngine __iter__ method is overridden so that each of these subclasses, when iterated over, produces child instances of the next smallest EventEngine subclass. Iterating on a Month produces Weeks, iterating on a Week produces Days and so on. As each parent produces its children, the events in the 'events' attribute get partitioned out to the children as appropriate to their date ranges. Right now I'm doing this as stupidly as possible: for each child 'c' in the parent, I loop over all the parent events, and append them to c.events if their date attribute falls within the child's date range: for e in self.events: if c.start = getattr(e,self.start_attr) c.stop: c.events.append(e) This is stupid for (at least) two reasons: 1) it evaluates the entire queryset and sticks it in memory with the first child instance, obviating the whole point of an iterable, and 2) it loops over the entire event list for every child, even though the list is already properly sorted by date, and we could break from the loop with the first event that falls outside the child's date range. Performance is important, as some madman could initialize a Year with a huge queryset, and do nested iterations all the way down to Minute. So I've got a few considerations: 1. The parent's events queryset should only be evaluated as much as is needed to yield one child at a time. 2. The parent's events queryset should not be duplicated as it is distributed among the children, ie it should make references and not copies (I don't know how to make sure this happens). 3. I don't want to empty the parent's 'events' list as it is distributed among the children, as other methods depend on the list being there. 4. The events attribute of the 'top level' instance is a django queryset, but it will be a list for all descendent instances (they can be nested arbitrarily deeply). This limits the number of functions available – ie you can't pop() a django queryset. At first I thought the bisect module was the way to go, but it is too tightly tied to integer list indices, and works very awkwardly when bisecting on datetime attributes. List slices produce copies, unless I'm mistaken. Something tells me that a plain old while loop with a break might do the trick, but I can't quite see it clear. Ideally this would be something that starts iterating where the date attribute falls into the right range, and then stops iterating as soon as it passes out of that range. Probably I'll have to settle for just one or the other, but one can dream. Thanks for reading all this. I'm hoping that all the restrictions and conditions will make the solution more obvious, rather than less obvious, to those who know more than I... --Eric ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] __iter__ loops, partitioning list among children
On Sat, Aug 23, 2008 at 6:47 AM, Eric Abrahamsen [EMAIL PROTECTED] wrote: At first I thought the bisect module was the way to go, but it is too tightly tied to integer list indices, and works very awkwardly when bisecting on datetime attributes. I'm not sure what the problem is with bisect (to find the starting point). Your list of model elements has integer indices. I think you have to write a __cmp__ method for your model class that compares on the datetime attribute, then it should work. You can also create a list of (key, model) and sort/search that. http://www.mail-archive.com/[EMAIL PROTECTED]/msg189443.html List slices produce copies, unless I'm mistaken. List slices copy the references in the list, not the values. I.e. it is not a deep copy. So you will have only one copy of each model instance even if you slice up the list. So, unless your lists are very large or you have many levels in your hierarchy, this might work. Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] For Loops and nested loops
Umesh Singhal wrote:
Hi im still relatively new to python and i am designing a
multiplication table that enables a user to input the size of the
times table unfortunately ive stumbled on the nested loops this is
what i have right now:
a=raw_input('please enter a number')
b=int(a)
n=b+1
for row in range(1, n):
for col in range(1, n):
print %3d % (row * col),
print
the input which comes out is:
12345
2468 10
369 12 15
48 12 16 20
5 10 15 20 25
however i need something more on the lines of:
| 2 3 4 5
==
2 | 4 6 8 10
3 | 6 9 12 15
4 | 8 12 16 20
5 | 10 15 20 25
does anyone know what i need the third nested for loop to be ? to make
it like the above example. Pleasee help me !!
I could write the program for you but I'd rather prod you into working
it out yourself as I think you will learn more in the process.
What code would you write to generate the first line? It is a loop, but
not nested.
At the beginning of each row you want to print the row number. What one
statement would you add and where would you put it to do that.
BTW I would find your questions and comments easier to read if you
divided sentences with capitalization and punctuation.
Be sure to reply-all.
--
Bob Gailer
Chapel Hill NC
919-636-4239
When we take the time to be aware of our feelings and
needs we have more satisfying interatctions with others.
Nonviolent Communication provides tools for this awareness.
As a coach and trainer I can assist you in learning this process.
What is YOUR biggest relationship challenge?
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Re: [Tutor] For Loops and nested loops
On Sat, Aug 16, 2008 at 06:33:42AM +0100, Umesh Singhal wrote:
Hi im still relatively new to python and i am designing a multiplication
table that enables a user to input the size of the times table unfortunately
ive stumbled on the nested loops this is what i have right now:
Is this a homework assignment? Forgive me if it's not, but somehow
it feels like the sort of thing a teacher would assign. At least,
I've been known to give my programming students things like it
before when they were just starting out.
a=raw_input('please enter a number')
b=int(a)
n=b+1
for row in range(1, n):
remember what n means in range(1, n). You may have a fencepost
error (off-by-one), depending on what you intended to happen here.
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[EMAIL PROTECTED] | to hunt for Tupperware.
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Re: [Tutor] For Loops and nested loops
On Sat, 2008-08-16 at 18:07 +0200, [EMAIL PROTECTED] wrote:
Message: 1
Date: Sat, 16 Aug 2008 06:33:42 +0100
From: Umesh Singhal [EMAIL PROTECTED]
Subject: [Tutor] For Loops and nested loops
To: tutor@python.org
Message-ID: [EMAIL PROTECTED]
Content-Type: text/plain; charset=windows-1252
Hi im still relatively new to python and i am designing a
multiplication table that enables a user to input the size of the
times table unfortunately ive stumbled on the nested loops this is
what i have right now:
a=raw_input('please enter a number')
b=int(a)
n=b+1
for row in range(1, n):
for col in range(1, n):
print %3d % (row * col),
print
the input which comes out is:
12345
2468 10
369 12 15
48 12 16 20
5 10 15 20 25
however i need something more on the lines of:
| 2 3 4 5
==
2 | 4 6 8 10
3 | 6 9 12 15
4 | 8 12 16 20
5 | 10 15 20 25
does anyone know what i need the third nested for loop to be ? to make
it like the above example. Pleasee help me !!
You don't need to use third nested loop, your two nested loop is enough.
First, however, you need to think first, how you'd generate the output.
Following your thinking pattern, I'd do it like this:
#1
| 2 3 4 5
#2
| 2 3 4 5
==
2 |
#3
| 2 3 4 5
==
2 | 4
#4
| 2 3 4 5
==
2 | 4 6
#5
| 2 3 4 5
==
2 | 4 6 8
#6
| 2 3 4 5
==
2 | 4 6 8 10
#7
| 2 3 4 5
==
2 | 4 6 8 10
3 |
#8 etc
Do you see how you could generate the table headings?
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Re: [Tutor] For Loops and nested loops
PLEASE REPLY TO THE GROUP NOT JUST ME. Did you miss my request for that
(reply-all)?
Umesh Singhal wrote:
Hi Bob,
unfortunately when i pasted in the code it seems to have gone wrong
this is how it is at the moment with the correct indentation for the
nested loop:
code:
a=raw_input('please enter a number')
b=int(a)
n=b+1
for row in range(1, n):
for col in range(1, n):
print "%3d " % (row *
col),
print
I am also unaware of what code I would need to enter to enable the row
to have the value selected, if you could please tell me as I will
understand it more if i see the code infront of me
thank you
Umesh Singhal
How did you get this much code written and not be able to figure that
out?
Put something like
print "%3d |" % row,
between the 2 for statements.
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Re: [Tutor] While Loops and Modules
Greetings,
On Dec 6, 2007 12:44 AM, earlylight publishing
[EMAIL PROTECTED] wrote:
Hello again to all the wonderfully helpful folks on this list. Today I did
my Google homework and I found this neat bit of code for a countdown timer.
import time
import threading
class Timer(threading.Thread):
def __init__(self, seconds):
self.runTime = seconds
threading.Thread.__init__(self)
def run(self):
time.sleep(self.runTime)
print Buzzz!!! Time's up!
t = Timer(30)
t.start()
I don't understand large chunks of it (don't know what threading, self, or
__init__ mean) but that's not important at the moment. It works and I will
learn the vocab eventually.
That is a good start! Get it working first, then figure it out later. 8^D
I also wrote this bit of code for a math challenge which comes in the next
part of my game.
import random
startNum = random.choice(range(1, 9))
newNum = startNum + 7
score = 0
print 'Start with the number ', startNum, '. Then continuously add 7 to
that number until the timer runs out. You have 30 seconds.'
answer = int(raw_input('Enter your answer: '))
if newNum == answer:
print 'That is correct! Keep going.'
score = score + 5
print 'Your score is ', score
else:
print 'That is incorrect. Please try again.'
I understand this part just fine 'cause I actually wrote it myself.
A couple of things which may help you when you're testing/debugging
your programs:
type(object)
dir(object)
Play with those in the interactive interpreter to see what they do, for example:
a = 7
type(a)
type 'int'
a = time
type(a)
type 'str'
import random
dir(random)
['BPF', 'LOG4', 'NV_MAGICCONST', 'RECIP_BPF', 'Random',
'SG_MAGICCONST', 'SystemRandom', 'TWOPI', 'WichmannHill',
'_BuiltinMethodType', '_MethodType', '__all__', '__builtins__',
'__doc__', '__file__', '__name__', '_acos', '_cos', '_e', '_exp',
'_hexlify', '_inst', '_log', '_pi', '_random', '_sin', '_sqrt',
'_test', '_test_generator', '_urandom', '_warn', 'betavariate',
'choice', 'expovariate', 'gammavariate', 'gauss', 'getrandbits',
'getstate', 'jumpahead', 'lognormvariate', 'normalvariate',
'paretovariate', 'randint', 'random', 'randrange', 'sample', 'seed',
'setstate', 'shuffle', 'uniform', 'vonmisesvariate', 'weibullvariate']
etc.
Another little trick I use to watch the values of variables and set breakpoints:
print variable_Name
raw_input(Pause)
I just insert those two lines after each variable I want to watch (perhaps
to see if it is actually doing what I think it is supposed to be doing?).
What I need to do now is put these two parts together so that the player
will keep adding 7 to the starting number for 30 seconds then the loop
breaks. I know I need a loop of some sort and I'm guessing it's a 'while'
sort of thing. I couldn't find what I was looking for when I Googled. I'm
not even sure I knew the right search terms. Does anyone know how I'd
combine these two modules to make it work?
while True: or while 1: do the same thing, and they are a generic infinite loop.
You can use the keyword break somewhere inside the loop to break out of it.
When you figure out what condition must be met to quit the while loop,
you can replace the True or 1 with your condition.
For example, working with the snippet you supplied:
import random
import time
import threading
class Timer(threading.Thread):
def __init__(self, seconds):
self.runTime = seconds
threading.Thread.__init__(self)
def run(self):
time.sleep(self.runTime)
print Buzzz!!! Time's up!
t = Timer(30)
startNum = random.choice(range(1, 9))
newNum = startNum + 7
score = 0
t.start()
print 'Start with the number ', startNum, '. Then continuously add 7
to that number until the timer runs out. You have 30 seconds.'
while 1:
answer = int(raw_input('Enter your answer: '))
if newNum == answer:
print 'That is correct! Keep going.'
score = score + 5
print 'Your score is ', score
newNum += 7
else:
print 'That is incorrect. Please try again.'
That isn't quite working as it should, but I only added a couple of lines
and did the requisite indentation for the while loop. It might be enough
to keep you going for a wee bit?
Happy Programming!
--
b h a a l u u at g m a i l dot c o m
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[Tutor] While Loops and Modules
Hello again to all the wonderfully helpful folks on this list. Today I did my
Google homework and I found this neat bit of code for a countdown timer.
import time
import threading
class Timer(threading.Thread):
def __init__(self, seconds):
self.runTime = seconds
threading.Thread.__init__(self)
def run(self):
time.sleep(self.runTime)
print Buzzz!!! Time's up!
t = Timer(30)
t.start()
I don't understand large chunks of it (don't know what threading, self, or
__init__ mean) but that's not important at the moment. It works and I will
learn the vocab eventually.
I also wrote this bit of code for a math challenge which comes in the next
part of my game.
import random
startNum = random.choice(range(1, 9))
newNum = startNum + 7
score = 0
print 'Start with the number ', startNum, '. Then continuously add 7 to that
number until the timer runs out. You have 30 seconds.'
answer = int(raw_input('Enter your answer: '))
if newNum == answer:
print 'That is correct! Keep going.'
score = score + 5
print 'Your score is ', score
else:
print 'That is incorrect. Please try again.'
I understand this part just fine 'cause I actually wrote it myself.
What I need to do now is put these two parts together so that the player will
keep adding 7 to the starting number for 30 seconds then the loop breaks. I
know I need a loop of some sort and I'm guessing it's a 'while' sort of thing.
I couldn't find what I was looking for when I Googled. I'm not even sure I
knew the right search terms. Does anyone know how I'd combine these two
modules to make it work?
-
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[Tutor] Infinite Loops (and threads)
Hi all, Just a quick question, really. Is there any good way to have an infinite loop in a program, without said infinite loop eating up the CPU? I've tried the trick of adding a pause (time.sleep(0.01)) somewhere in the loop, and this appears to have worked on a basic infinite loop, but this doesn't appear to work for two separate infinite loops (in threads). Thanks in advance. -- Regards, Jonathan McManus signature.asc Description: This is a digitally signed message part ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Infinite Loops (and threads)
Jonathan McManus wrote: Hi all, Just a quick question, really. Is there any good way to have an infinite loop in a program, without said infinite loop eating up the CPU? I've tried the trick of adding a pause (time.sleep(0.01)) somewhere in the loop, and this appears to have worked on a basic infinite loop, but this doesn't appear to work for two separate infinite loops (in threads). You would have to put a sleep in each thread. Why are you using infinite loops? Are you implementing some kind of polling loop? Often there are better alternatives, either an event notification or some kind of lock. If you post some details of why you want to do this we may be able to help you find a better way. Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Infinite Loops (and threads)
Kent Johnson wrote:
Jonathan McManus wrote:
Hi all,
Just a quick question, really. Is there any good way to have an infinite
loop in a program, without said infinite loop eating up the CPU? I've
tried the trick of adding a pause (time.sleep(0.01)) somewhere in the
loop, and this appears to have worked on a basic infinite loop, but this
doesn't appear to work for two separate infinite loops (in threads).
You would have to put a sleep in each thread.
Why are you using infinite loops? Are you implementing some kind of
polling loop? Often there are better alternatives, either an event
notification or some kind of lock. If you post some details of why you
want to do this we may be able to help you find a better way.
Kent
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Kent et. al.,
I'm writing something that has to do with sockets.
I need to recv any incoming packets from the socket.
I will have potentially hundreds of separate sockets open in a single
application.
I was just going to create a thread for each, so I could receive from
them separately.
Alternately, I figured I could read from each socket in sequence if I
could get the recv method to not block until it gets input,
so I tried this,
#code
self.conn.setblocking(False)
info = self.conn.recv(8000)#this should read everything.
# code
where conn is connected to another computer already,
and I get the following error:
(Verbatim except for line 3, changed to hide username/password)
Traceback (most recent call last):
File C:\Python Scripts\AIM Connection Server\toc2.py, line 199, in ?
toc.login('---username---','---password---')
File C:\Python Scripts\AIM Connection Server\toc2.py, line 116, in login
print self.getFlap()
File C:\Python Scripts\AIM Connection Server\toc2.py, line 93, in
getFlap
info = self.conn.recv(8000)#this should read everything.
error: (10035, 'The socket operation could not complete without blocking')
Do I misunderstand what blocking is?
It seems to me that blocking would mainly apply to inputs.
(My understanding is that 'blocking' means when you call 'recv' it will
return '' if it didn't receive anything.)
I'd appreciate any links that I could read up on, or any advice on how
to make socket inputs with event notification, as Kent mentioned earlier.
Basically, as Kent said, I have a polling loop, and I am not sure what
the alternative is to threads.
Thanks,
-Luke
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Re: [Tutor] Infinite Loops (and threads)
On 24/12/06, Luke Paireepinart [EMAIL PROTECTED] wrote:
Kent Johnson wrote:
Jonathan McManus wrote:
Hi all,
Just a quick question, really. Is there any good way to have an
infinite
loop in a program, without said infinite loop eating up the CPU? I've
tried the trick of adding a pause (time.sleep(0.01)) somewhere in the
loop, and this appears to have worked on a basic infinite loop, but
this
doesn't appear to work for two separate infinite loops (in threads).
You would have to put a sleep in each thread.
Why are you using infinite loops? Are you implementing some kind of
polling loop? Often there are better alternatives, either an event
notification or some kind of lock. If you post some details of why you
want to do this we may be able to help you find a better way.
Kent
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Kent et. al.,
I'm writing something that has to do with sockets.
I need to recv any incoming packets from the socket.
I will have potentially hundreds of separate sockets open in a single
application.
I was just going to create a thread for each, so I could receive from
them separately.
Alternately, I figured I could read from each socket in sequence if I
could get the recv method to not block until it gets input,
so I tried this,
#code
self.conn.setblocking(False)
info = self.conn.recv(8000)#this should read everything.
# code
where conn is connected to another computer already,
and I get the following error:
(Verbatim except for line 3, changed to hide username/password)
Traceback (most recent call last):
File C:\Python Scripts\AIM Connection Server\toc2.py, line 199, in ?
toc.login('---username---','---password---')
File C:\Python Scripts\AIM Connection Server\toc2.py, line 116, in
login
print self.getFlap()
File C:\Python Scripts\AIM Connection Server\toc2.py, line 93, in
getFlap
info = self.conn.recv(8000)#this should read everything.
error: (10035, 'The socket operation could not complete without blocking')
Do I misunderstand what blocking is?
It seems to me that blocking would mainly apply to inputs.
(My understanding is that 'blocking' means when you call 'recv' it will
return '' if it didn't receive anything.)
I'd appreciate any links that I could read up on, or any advice on how
to make socket inputs with event notification, as Kent mentioned earlier.
Basically, as Kent said, I have a polling loop, and I am not sure what
the alternative is to threads.
Thanks,
-Luke
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Well I've been doing some networking stuff in stackless myself recently and
I would probably do something like this:
import select
import stackless
import socket
def get_data(sock):
sock.setblocking(0)
poller = select.poll()
poller.register(sock, select.POLLIN)
while True:
if poller.poll(0):
sock.recv(1024)
stackless.schedule()
stackless.tasklet(get_data)(socket.socket(socket.AF_INET, socket.SOCK_DGRAM
))
stackless.run()
stackless thread things are really low on resources so you can run tens of
thousands without too much trouble.
HTH,
Adam.
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Re: [Tutor] Infinite Loops (and threads)
Luke Paireepinart [EMAIL PROTECTED] On Sun, 24 Dec 2006 10:02:19 -0600 wrote: Kent Johnson wrote: Kent et. al., I'm writing something that has to do with sockets. I need to recv any incoming packets from the socket. I will have potentially hundreds of separate sockets open in a single application. I was just going to create a thread for each, so I could receive from them separately. Alternately, I figured I could read from each socket in sequence if I could get the recv method to not block until it gets input, so I tried this, snip Thanks, -Luke Use import select and read about it for more information (i.e. help(select) within Python shell). I advice you (and others interested in writing Python code dealing with sockets) *very strongly* to read the following: http://www.amk.ca/python/howto/sockets/ (Currently, I'm having trouble accessing that URL. I don't know if it's my ISP or the the site is down.) I hope that helps. Ziyad. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Infinite Loops (and threads)
Luke Paireepinart wrote: Kent et. al., I'm writing something that has to do with sockets. I need to recv any incoming packets from the socket. I will have potentially hundreds of separate sockets open in a single application. I was just going to create a thread for each, so I could receive from them separately. Yes, that is one way to do it - make a thread for each socket and use blocking I/O. Then each thread will block until data is available. This avoids the kind of busy wait loop the OP described. Alternately, I figured I could read from each socket in sequence if I could get the recv method to not block until it gets input, That is another good approach. You might want to look at Twisted or Medusa, they are both server frameworks that use asynchronous, non-blocking I/O to manage multiple sockets in a single thread: http://twistedmatrix.com/trac/ http://www.nightmare.com/medusa/ Do I misunderstand what blocking is? It seems to me that blocking would mainly apply to inputs. Usually, though output can block too. (My understanding is that 'blocking' means when you call 'recv' it will return '' if it didn't receive anything.) No; with a blocking socket, recv() will not return until data is available; with a non-blocking socket recv() will raise an exception if data is not available. Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] foreach loops
Does python have foreach loops? I don't see any mention of them in the docs. Am I going to have to use Perl (gasp!) if I want my beloved foreach loop? Its called a for loop in Python... Or is there some extra magic in the Perl version that I'm missing? Alan G. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] foreach loops
I was thinking more along the lines of this:
A C++ for loop:
This is exactly NOT a foreach loop, its a vanilla for loop.
#include iostream
using std::cout;
int main() {
for (int i = 0; i 10; i++) {
cout i \n;
}
for i in range(10): print i
Alan G.
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[Tutor] foreach loops
Does python have foreach loops? I don't see any mention of them in the docs. Am I going to have to use Perl (gasp!) if I want my beloved foreach loop? -Chris ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] foreach loops
Does python have foreach loops? I don't see any mention of them in the docs. Am I going to have to use Perl (gasp!) if I want my beloved foreach loop? Can you show an example of a Perl foreach loop? Perhaps someone can help translate it into idiomatic Python. Good luck! ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] foreach loops
Danny Yoo wrote:
Does python have foreach loops? I don't see any mention of them in the
docs. Am I going to have to use Perl (gasp!) if I want my beloved
foreach loop?
Can you show an example of a Perl foreach loop? Perhaps someone can help
translate it into idiomatic Python.
It seems to me that foreach is the same as the python 'for' loop
#-- perl code
@myNames = ('Larry', 'Curly', 'Moe');
print Who's on the list:\n; foreach (@myNames) {
print $_ . \n;
}
#--- python code:
names = ['Larry','Curly','Moe']
print Who's on the list?\n
for x in mynames:
print x+'\n'
#
Am I missing the point here?
-Luke
Good luck!
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Re: [Tutor] foreach loops
Christopher Spears wrote:
Hmmm...Perl is probably a bad example. My apologies.
I was thinking more along the lines of this:
A C++ for loop:
#include iostream
using std::cout;
int main() {
for (int i = 0; i 10; i++) {
cout i \n;
}
return 0;
}
for i in range(10):
print i+'\n'
that does the same thing as
a = [0,1,2,3,4,5,6,7,8,9]
for i in a:
print i+'\n'
or
a = range(10)
for i in a:
print i+'\n'
Python's 'for' loop is not really meant as an iterator over a list of
numbers
so this feature isn't built into the loop itself, you have to use the
range function,
which just generates a list of numbers to iterate over.
Perhaps you should read an introductory Python tutorial.
Any one of them should cover the types of questions that people from
other languages have about Python.
It sounds like you know how to program already, so the 'python for
non-programmers' type of tutorial
may not be best-suited to you, but just look around.
If you have any more questions I'd be happy to answer them,
as would the rest of the list, I'm sure.
HTH,
-Luke
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Re: [Tutor] foreach loops
Christopher Spears wrote:
Hmmm...Perl is probably a bad example. My apologies.
I was thinking more along the lines of this:
A C++ for loop:
#include iostream
using std::cout;
int main() {
for (int i = 0; i 10; i++) {
cout i \n;
}
return 0;
}
The same functionality can be provided using python for and the range()
function, like:
for i in range(0, 10):
print i
Though because of the way python works you don't need to use this type
of loop anywhere near as often as in other languages. For example in
java (and c++, but my c++ is so rusty I'm not going embarrass myself
trying to write an example) you're constantly doing things like looping
over an array:
public void main(String[] args) {
int[] foo;
/* then later after foo has been initialized to whatever: */
for (int i=0; ifoo.length; i++) {
System.out.println(foo[i]);
}
}
The equivalent code in python is much cleaner, after foo has been
initialized to whatever:
for each in foo:
print each
Hope this helps,
Jordan Greenberg
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Re: [Tutor] no loops
def increment(time, seconds): time.seconds = time.seconds + seconds while time.seconds = 60: time.seconds = time.seconds - 60 time.minutes = time.minutes + 1 Tale a look at what this loop is doing. Think about its purpose. If you werre doing this with paper and pencil would you really use iteration? Think division As an exercise, rewrite this function so that it doesn't contain any loops. I have been staring at this function and drawing a blank. Something tells me that I need to use iteration, but I am not sure how I could implement it. The loops are implementing a mathematical function which doesn't need a loop. Look at the division and modulo operators. Alan Gauld Author of the Learn to Program web site http://www.freenetpages.co.uk/hp/alan.gauld ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] no loops
I am working on another problem from How To Think Like A Computer Scientist. Here is a function: def increment(time, seconds): time.seconds = time.seconds + seconds while time.seconds = 60: time.seconds = time.seconds - 60 time.minutes = time.minutes + 1 while time.minutes = 60: time.minutes = time.minutes - 60 time.hours = time.hours + 1 Here is the function in action: from time import * atime = Time() atime.hours = 1 atime.minutes = 60 atime.seconds = 120 printTime(atime) 1:60:120 increment(atime,1) printTime(atime) 2:2:1 Now the exercise is: As an exercise, rewrite this function so that it doesn't contain any loops. I have been staring at this function and drawing a blank. Something tells me that I need to use iteration, but I am not sure how I could implement it. -Chris ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] no loops
Christopher Spears schrieb: IF you know that it's 2 seconds after midnight, how many hours, minutes, seconds after midnight ist this. If you should compute this by hand, how would you proceed? Best wishes, Gregor I am working on another problem from How To Think Like A Computer Scientist. Here is a function: def increment(time, seconds): time.seconds = time.seconds + seconds while time.seconds = 60: time.seconds = time.seconds - 60 time.minutes = time.minutes + 1 while time.minutes = 60: time.minutes = time.minutes - 60 time.hours = time.hours + 1 Here is the function in action: from time import * atime = Time() atime.hours = 1 atime.minutes = 60 atime.seconds = 120 printTime(atime) 1:60:120 increment(atime,1) printTime(atime) 2:2:1 Now the exercise is: As an exercise, rewrite this function so that it doesn't contain any loops. I have been staring at this function and drawing a blank. Something tells me that I need to use iteration, but I am not sure how I could implement it. -Chris ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] no loops
On 12/07/06, Christopher Spears [EMAIL PROTECTED] wrote: Now the exercise is: As an exercise, rewrite this function so that it doesn't contain any loops. I have been staring at this function and drawing a blank. Something tells me that I need to use iteration, but I am not sure how I could implement it. Hi Chris, You are using iteration. That's what loops are :-) Perhaps you meant to say recursion, which is where a function calls itself. You could solve this recursively, but I think Gregor's comment is closer to what they want you to do. -- John. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] no loops
--- John Fouhy [EMAIL PROTECTED] wrote: On 12/07/06, Christopher Spears [EMAIL PROTECTED] wrote: Now the exercise is: As an exercise, rewrite this function so that it doesn't contain any loops. I have been staring at this function and drawing a blank. Something tells me that I need to use iteration, but I am not sure how I could implement it. Hi Chris, You are using iteration. That's what loops are :-) Perhaps you meant to say recursion, which is where a function calls itself. You could solve this recursively, but I think Gregor's comment is closer to what they want you to do. -- John. I agree with Gregor and John. What makes the problem difficult is the fact that time is represented using 3 different units of measure: hours, minutes, and seconds. The math becomes much simpler if you convert the time value to a single unit (such as seconds). But it doesn't have to be seconds. I recall seeing one database that stores time as fractional hours where a minute is worth 1/60 of an hour and a second is worth 1/3600 of an hour. In other words, 1:15 is stored as 1.25 hours, 4:30 is stored as 4.5 hours, and so forth. Converting from (hours, minutes, seconds) to fractional hours is pretty easy, but going the other way is not so simple. __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] no loops
Christopher Spears wrote: I am working on another problem from How To Think Like A Computer Scientist. Here is a function: def increment(time, seconds): time.seconds = time.seconds + seconds while time.seconds = 60: time.seconds = time.seconds - 60 time.minutes = time.minutes + 1 while time.minutes = 60: time.minutes = time.minutes - 60 time.hours = time.hours + 1 Here is the function in action: from time import * atime = Time() atime.hours = 1 atime.minutes = 60 atime.seconds = 120 printTime(atime) 1:60:120 increment(atime,1) printTime(atime) 2:2:1 Now the exercise is: As an exercise, rewrite this function so that it doesn't contain any loops. I have been staring at this function and drawing a blank. Something tells me that I need to use iteration, but I am not sure how I could implement it. take a look at the divmod built-in function. -- Bob Gailer 510-978-4454 ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] for loops over multiple lists of the same length
I feel like there should be a better way to do this process: Can you please help? (This is trivial example code I created off the top of my head, but the same concept that I am trying to do elsewhere.) class Person(object): def __init__(self, first_name, age, fav_color): self.first_name = first_name self.age = age self.fav_color = fav_color first_names = ['emily', 'john', 'jeremy', 'juanita'] ages = [6, 34, 1, 19] colors = ['blue', 'orange', 'green', 'yellow'] ageIter = ages.iter() colorIter = colors.iter() people = [Person(name, ageIter.next(), colorIter.next()) for name in first_names] print people any suggestions, please? Emily ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] for loops over multiple lists of the same length
Emily Fortuna wrote: I feel like there should be a better way to do this process: Can you please help? (This is trivial example code I created off the top of my head, but the same concept that I am trying to do elsewhere.) class Person(object): def __init__(self, first_name, age, fav_color): self.first_name = first_name self.age = age self.fav_color = fav_color first_names = ['emily', 'john', 'jeremy', 'juanita'] ages = [6, 34, 1, 19] colors = ['blue', 'orange', 'green', 'yellow'] ageIter = ages.iter() colorIter = colors.iter() people = [Person(name, ageIter.next(), colorIter.next()) for name in first_names] print people any suggestions, please? The builtin function zip() does this: people = [Person(name, age, color) for name, age color in zip(first_names, ages, colors)] Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] for loops over multiple lists of the same length
+++ Emily Fortuna [22-06-06 13:22 -0400]: | I feel like there should be a better way to do this process: | Can you please help? | (This is trivial example code I created off the top of my head, but the | same concept that I am trying to do elsewhere.) | | class Person(object): | def __init__(self, first_name, age, fav_color): | self.first_name = first_name | self.age = age | self.fav_color = fav_color | | first_names = ['emily', 'john', 'jeremy', 'juanita'] | ages = [6, 34, 1, 19] | colors = ['blue', 'orange', 'green', 'yellow'] | | ageIter = ages.iter() | colorIter = colors.iter() | people = [Person(name, ageIter.next(), colorIter.next()) for name in | first_names] | | print people | | any suggestions, please? | Emily data = [['emily',6,'blue'],['jhon',34,'orange'],['jeremy',1,'green'],['junita',19,'yellow']] people = [Person(name,age,color) for name,age,color in data] Regards, Shantanoo -- Eliminate guilt. Don't fiddle expenses, taxes or benefits, and don't cheat colleagues. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] for loops
* josip [EMAIL PROTECTED] [2006-04-11 09:13]: I have problem with this question. Can someone show me the code and than explain it? Write a Python program to print out the following shape. You are expected to use two for loops (these must be nested) to solve this problem. output: * * * * * * * * * * * * * * That looks a lot like homework. If you have a specific question about a _part_ of code _you_ have written, we'll be glad to help out explaining those specifics. We generally try to stay away from doing the work for you :-) -- David Rock [EMAIL PROTECTED] ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] for loops
Write a Python program to print out the following shape. You are expected to use two for loops (these must be nested) to solve this problem. output: * * * * * * * * * * * * * * That looks a lot like homework. I agree and very poor homework too. I certainly wouldn't expect to use two for loops, I'd only use one. (And that assumes the more general problem of drawing an arbitrary sized square, for the specific case I'd use a single print statement and triple quoted string!) Any homework which implies that only one design is acceptable is a bad assignment in my book! We generally try to stay away from doing the work for you :-) But the advice stays good. Tell us how far you got and what's sticking you and we will try to help... Alan G Author of the learn to program web tutor http://www.freenetpages.co.uk/hp/alan.gauld ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] for loops and exceptions
Matthew White wrote: Hello, From a general style and/or programmatic perspective, which is a better way to write this bit of code? Hmm, neither? try: (dn, attrs) = conn.search_s(search_base, search_scope, search_filter, search_attrs): except Exception, e: warn_the_user(e) do_something_useful() for (name, data) in (dn, attrs): print '%s' % (name) for key, value in data.iteritems(): print '%s = %s' % (key, value) This will run the for loop even if you get an exception. I think the for loop is buggy, too, it is different from the one below. OR try: for dn, attrs in conn.search_s(search_base, search_scope, search_filter, search_attrs): print dn for key, value in attrs.iteritems(): print '\t%s = %s' % (key, value) print except Exception, e: warn_the_user(e) do_something_useful This might be OK. It will catch exceptions in the for loop, which you may or may not want. If this code is at a low level of your program, it's best to only catch expected exceptions, and let unexpected exceptions propagate to a higher level. At the higher level, you can have a generic except block that reports the error and moves on. This is often in a top-level loop or event handler. Your code has elements of both - code that does real work with a generic except block that reports errors. Anyway here is a construction that is very useful for catching just the exceptions you expect to see from a bit of code, while running the rest of the code outside of the try block. try: (dn, attrs) = conn.search_s(search_base, search_scope, search_filter, search_attrs): except ConnectionError, e: warn_the_user(e) do_something_useful() else: print dn for key, value in attrs.iteritems(): print '\t%s = %s' % (key, value) print The idea is to put as little code as possible in the scope of the try, and to catch as few exceptions as possible. If no exception is raised, the else: block will run. If there is an exception in that code, it will propagate to a higher level. Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] for loops and exceptions
Hello, From a general style and/or programmatic perspective, which is a better way to write this bit of code? try: (dn, attrs) = conn.search_s(search_base, search_scope, search_filter, search_attrs): except Exception, e: warn_the_user(e) do_something_useful() for (name, data) in (dn, attrs): print '%s' % (name) for key, value in data.iteritems(): print '%s = %s' % (key, value) OR try: for dn, attrs in conn.search_s(search_base, search_scope, search_filter, search_attrs): print dn for key, value in attrs.iteritems(): print '\t%s = %s' % (key, value) print except Exception, e: warn_the_user(e) do_something_useful Personally I like the second method more. To my eyes it is compact and efficient. Coming from a perl background I tend to like to get very compact, which can be an impediment to code readability. As I get started with python I want to make sure that I don't repeat the same mistakes and let too many perl-isms creep into my python code. -mtw -- Matthew White - District Systems Administrator Tigard/Tualatin School District 503.431.4128 The greatest thing in this world is not so much where we are, but in what direction we are moving. -Oliver Wendell Holmes ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] nested loops
Is there any way more efficient for run a nested loop? -- for a in list_a: for b in list_b: if a == b: break ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] nested loops
On Mon, 22 Aug 2005, Kent Johnson wrote: Is there any way more efficient for run a nested loop? -- for a in list_a: for b in list_b: if a == b: break Hi Jonas, Depends on what we're trying to do. Is it necessary to have a nested loop here? What kind of problem is this trying to solve? If the question is: are any elements in list_a shared in list_b?, then yes, we can avoid nested loops altogether. If we're concerned about efficiency, we can take advanatage of dictionaries, or use something like the 'set' data structure. http://www.python.org/doc/lib/module-sets.html ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] while loops
Thanks for the help guys. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
