Re: [Tutor] Beginner Question
On Wed, 10/23/13, Steven D'Aprano st...@pearwood.info wrote: Subject: Re: [Tutor] Beginner Question To: tutor@python.org Date: Wednesday, October 23, 2013, 5:27 AM On Tue, Oct 22, 2013 at 04:25:59PM +0200, Sven Hennig wrote: Hello, I would like to learn a programming language and have decided to use Python. I have some programming experience and doing well in Python. What really causes me problems is OOP. I'm just dont get it... I'm missing a really Practical example. In every book I've read are the examples of such Class Dog and the function is bark. Has anyone an OOP example for me as it is really used in real code, so I can better understand the concept? I do not know why this is so hard for me. I can sympathise. You wouldn't believe how long it took me to really grok object-oriented programming. I just didn't get it, until I started thinking of OOP as being just syntax for keeping functions (called methods) close to the data they belong with. There is more to OOP than that, but that was my first step: OOP helps you keep your functions close to the data they work with. snip That's all you need to know to start using object oriented programming in Python! Many operations are implemented as methods, for instance strings have upper and lower methods, lists have append and remove methods, and many more. You'll soon learn the operations like len() that aren't methods, but old-school functions. == This reminded me of a text by Guido van Rossum (I can't find the original page): http://effbot.org/pyfaq/why-does-python-use-methods-for-some-functionality-e-g-list-index-but-functions-for-other-e-g-len-list.htm So the built-in 'len()' is *really* a function, but calls to len() implemented by __len__ are method calls *disguised* as function calls? I sometimes find it easier to write calls to special methods the normal way, e.g. instead of x + y just write it like x.__add__(y) This makes special methods more like other methods and therefore easier to understand, to me at least. Albert-Jan PS: sorry about the lack of quoting. Yahoo mail was upgraded and now all sorts of stuff stops working, times out, etc. ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Beginner Question
On 23 October 2013 08:58, Albert-Jan Roskam fo...@yahoo.com wrote: So the built-in 'len()' is *really* a function, but calls to len() implemented by __len__ are method calls *disguised* as function calls? I sometimes find it easier to write calls to special methods the normal way, e.g. instead of x + y just write it like x.__add__(y) This makes special methods more like other methods and therefore easier to understand, to me at least. Please don't do that. Firstly it looks horrible. Secondly they're not equivalent. The equivalent of x + y is operator.add(x, y) but don't use that either. It's not easier to understand and it's less efficient. When you wrate a+b the interpreter actually calls a bunch of different methods: a.__add__(b), b.__radd__(a), a.__coerce__(b) etc. I don't know the full sequence and it's not consistent across Python implementations. Eryksun recently posted a good example showing how a == b is handled: https://mail.python.org/pipermail/tutor/2013-July/097110.html Oscar ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Beginner question on classes
On 23/10/13 08:25, Corinne Landers wrote: Hi guys, I need a bit of help. I'm writing a class, and in the main function I'm trying to say if this method gets called, do this. What you are actually doing is if the method returns a truth-like value do this. Not quite the same thing, but much easier! I'm trying things like: program = AnimalClass(x,y,z) for i in range(x): for j in range(y): for k in range(z): animal = program.animal() if animal: if isinstance(animal,moose): print(There is a moose here) The block below for k... needs more indentation and The final print needs yet another level of indentation... It's clearly not correct because it's giving me all sorts of grief, Could you be more specific? What kind of grief? Error messages? Then send the full message here. Your computer crashes? It doesn't print a message you expected? While you are at it which Python version and OS are you using? -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.flickr.com/photos/alangauldphotos ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Beginner question on classes
On 23 October 2013 08:25, Corinne Landers corinne.land...@live.com wrote: Hi guys, Hi Corrine, I need a bit of help. I'm writing a class, and in the main function I'm trying to say if this method gets called, do this. I'm trying things like: program = AnimalClass(x,y,z) for i in range(x): for j in range(y): for k in range(z): animal = program.animal() if animal: if isinstance(animal,moose): print(There is a moose here) It's clearly not correct because it's giving me all sorts of grief, but if anyone knows how to do this correctly I'd very much appreciate it! I'm sure someone will help you but you haven't really given enough information yet. Is the code you posted the whole of your program? If so please say so explicitly because it looks like only part of a program to me and you should show the whole code for anyone to understand what you're doing. Also you say that it is giving you grief but we need more than that. Is it showing an error message? If so please copy/paste the whole error message and traceback. Here's an example showing what happens when I run your program as shown above (saved into a file called tmp.py): $ python tmp.py File tmp.py, line 5 animal = program.animal() ^ IndentationError: expected an indented block What that error means is that you need to indent everything inside the 3rd for loop on line 5. Oscar ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Beginner question on classes
On 23/10/2013 03:25, Corinne Landers wrote: --/style/head body class='hmmessage'div dir='ltr'Hi guys,nbsp;divbr/divdivI need a bit of help.nbsp;/divdivI'm writing a class, and in the main function I'm trying to say if this method gets called, do this.nbsp;/divdivI'm trying things like:/divdivbr/divdivprogram = AnimalClass(x,y,z)/divdivfor i in range(x):/divdivnbsp; nbsp;for j in range(y):/divdivnbsp; nbsp; nbsp; for k in range(z):/divdivnbsp; nbsp; nbsp; animal = program.animal()/divdivnbsp; nbsp; nbsp; if animal:nbsp;/divdivnbsp; nbsp; nbsp; nbsp; nbsp; if isinstance(animal,moose):/divdivnbsp; nbsp; nbsp; nbsp; nbsp; print(There is a moose here)/divdivbr/divdivIt's clearly not correct because it's giving me all sorts of grief, but if anyone knows how to do this correctly I'd very much appreciate it!/divdivbr/divdivCorrine/divdivbr/div /div/body /html Hi, and welcome to Python, and to the Python tutor list. Please start by telling us what Python version you're using, and what OS. Please post here using a text message, not html, as many email programs (apparently including yours) cannot correctly convert the html to text. Your entire program fragment appears on one line in my newsreader. And people like me can see the html, but not display it. This is a text newsgroup. Studying other people's responses that do have html abilities, I can see that you did post an indented code fragment, so I'll copy that here and comment on it. program = AnimalClass(x,y,z) for i in range(x): for j in range(y): for k in range(z): animal = program.animal() if animal: if isinstance(animal,moose): print(There is a moose here) Your problem statement was: if this method gets called, do this No idea which of these is this method, nor what you intend by do this. And you needn't test whether it's being called, since presumably you're calling it. Usually, you test the return value of a method, but that's not what you're saying. Just looking at the code in isolation, I can see that you'll get an indentation error on the line assigning to animal. You have to indent the body of any for statement. Next, it appears you don't use i, j and k. So are you intending to just do the same thing x*y*z times? If so, then you just should use one loop, and multiple them together. Does program.animal() return the same value each time, or is it somehow supposed to guess the values of i, j, and k ? Is moose a class name, defined elsewhere that you didn't include? Then it ought to be capitalized, to make that obvious. It's just a convention, but following conventions will make your code easier to read. I know that many classes in the standard lib are not capitalized, but that's mostly because the names were established many many years ago, some perhaps before there was the ability to write user classes. Pep-8 is the place where such conventions are described. -- DaveA ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
[Tutor] Beginner Question
Hello, I would like to learn a programming language and have decided to use Python. I have some programming experience and doing well in Python. What really causes me problems is OOP. I'm just dont get it... I'm missing a really Practical example. In every book I've read are the examples of such Class Dog and the function is bark. Has anyone an OOP example for me as it is really used in real code, so I can better understand the concept? I do not know why this is so hard for me. Greetings Sven ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Beginner Question
On 22/10/13 15:25, Sven Hennig wrote: Hello, I would like to learn a programming language and have decided to use Python. I have some programming experience and doing well in Python. What really causes me problems is OOP. Don't worry this is common. The problem with OOP is that it only really becomes useful when you get to bigger programs than a beginner has typically met. So its value is not obvious. For some (slightly) more real world examples try the OOP page in my tutorial with examples using shapes and bank accounts. (see .sig) The other big area where it is used is in GUI programming. On-screen widgets like buttons, menus, sliders etc are naturally modelled as objects. You can then attach methods like onPress to a button or onMove() or position() to a slider. Then as you build your GUI screen you will have klots of instanmces of the objects, multiple buttons, labels, text fields etc. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.flickr.com/photos/alangauldphotos ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Beginner Question
On Tue, Oct 22, 2013 at 10:25 AM, Sven Hennig shenni...@googlemail.comwrote: Hello, I would like to learn a programming language and have decided to use Python. I have some programming experience and doing well in Python. What really causes me problems is OOP. I'm just dont get it... I'm missing a really Practical example. In every book I've read are the examples of such Class Dog and the function is bark . Has anyone an OOP example for me as it is really used in real code, so I can better understand the concept? I do not know why this is so hard for me. Greetings Sven The actual code I have is in PHP, so it's not exactly useful to post here, but I can give you an outline of a class I used and found useful. The class was created to help me manipulate network subnets in an interface to handle DHCP and DNS on a server. class subnet: def __init__(cidr): # Do some stuff with the CIDR notation of the subnet (1.2.3.0/24syntax) def netmask: # Calculate the netmask and return it (ie, 255.255.255.0) def first_ip: # Calculate and return the first IP in the range. def last_ip: # Calculate and return the last IP in the range def number_of_addresses: # Calculate the number of usable addresses in the range and return that value The benefit to me was that I could create an instance of the subnet object for a group (say, lab_1), and then pull out various information. Calling lab_1.first_ip() returns the first possible IP address. That was a lot more readable and a lot more concise than something like first_ip( 1.2.3.0/24). I hope this helps! Andy ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Beginner Question
On 22/10/2013 10:25, Sven Hennig wrote: Hello, I would like to learn a programming language and have decided to use Python. I have some programming experience and doing well in Python. What really causes me problems is OOP. I'm just dont get it... I'm missing a really Practical example. In every book I've read are the examples of such Class Dog and the function is bark. Has anyone an OOP example for me as it is really used in real code, so I can better understand the concept? I do not know why this is so hard for me. What you may not realize is you're already doing OOP, just by using the standard library. When you open a file (or many other things that can produce a stream of bytes), you get an instance of class file. When you use that instance, you're calling methods of that instance. So when you say: infile = open(myfile.txt,r) data = infile.readline() you're doing object oriented programming. You don't have to know what kind of thing infile is, you just have to know it has methods read(), readline(), close(), etc. When you want to write your own classes, or when you want to make a new class that's related but different from one of the thousands that are standard, that's when it gets interesting. As Alan says, GUI is one place where you'll be wrting your own classes, usually by deriving from one of the GUI library classes. At its most fundamental, a class is a description of how to create and how to manipulate instances. An instance has methods (functions), and attributes (data). When one class is derived from another, it can share some or most of the attributes and behavior of the parent class, but make changes. This helps avoid duplicating code when two things are similar. You're familiar with list and tuple. Those are built-in collection classes, supported explicitly by the language. But if you want your own collection, you may want to make a class for it. The Dog bark() example may seem silly, but a Dog has lots of other methods besides that one, and has lots of attributes (color, breed, health state, owner, etc.). In a sense those attributes are like a list within the Dog, but you want them to have nice names, instead of remembering that the 3rd one is owner. -- DaveA ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Beginner Question
Thank you! You guys helped me out alot. @Alan your website is great! Really clearly written. Especially the Things to remember part. If you have exercises for me or have a Website with exercises, bring it on. I think this is the best way to learn. 2013/10/22 Dave Angel da...@davea.name On 22/10/2013 10:25, Sven Hennig wrote: Hello, I would like to learn a programming language and have decided to use Python. I have some programming experience and doing well in Python. What really causes me problems is OOP. I'm just dont get it... I'm missing a really Practical example. In every book I've read are the examples of such Class Dog and the function is bark. Has anyone an OOP example for me as it is really used in real code, so I can better understand the concept? I do not know why this is so hard for me. What you may not realize is you're already doing OOP, just by using the standard library. When you open a file (or many other things that can produce a stream of bytes), you get an instance of class file. When you use that instance, you're calling methods of that instance. So when you say: infile = open(myfile.txt,r) data = infile.readline() you're doing object oriented programming. You don't have to know what kind of thing infile is, you just have to know it has methods read(), readline(), close(), etc. When you want to write your own classes, or when you want to make a new class that's related but different from one of the thousands that are standard, that's when it gets interesting. As Alan says, GUI is one place where you'll be wrting your own classes, usually by deriving from one of the GUI library classes. At its most fundamental, a class is a description of how to create and how to manipulate instances. An instance has methods (functions), and attributes (data). When one class is derived from another, it can share some or most of the attributes and behavior of the parent class, but make changes. This helps avoid duplicating code when two things are similar. You're familiar with list and tuple. Those are built-in collection classes, supported explicitly by the language. But if you want your own collection, you may want to make a class for it. The Dog bark() example may seem silly, but a Dog has lots of other methods besides that one, and has lots of attributes (color, breed, health state, owner, etc.). In a sense those attributes are like a list within the Dog, but you want them to have nice names, instead of remembering that the 3rd one is owner. -- DaveA ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Beginner Question
On 22/10/13 19:18, Sven Hennig wrote: Thank you! You guys helped me out alot. @Alan your website is great! Really clearly written. Especially the Things to remember part. Glad you like it. Someday (soon!) I'll get round to finishing the v3 version... So much to do, so little time! If you have exercises for me There are exercises but they are buried in the text. ie suggestions for the reader to try to extend the examples or to write other parallel examples for themselves. There is also a page with suggested projects near the end. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.flickr.com/photos/alangauldphotos ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Beginner Question
On Tue, Oct 22, 2013 at 04:25:59PM +0200, Sven Hennig wrote: Hello, I would like to learn a programming language and have decided to use Python. I have some programming experience and doing well in Python. What really causes me problems is OOP. I'm just dont get it... I'm missing a really Practical example. In every book I've read are the examples of such Class Dog and the function is bark. Has anyone an OOP example for me as it is really used in real code, so I can better understand the concept? I do not know why this is so hard for me. I can sympathise. You wouldn't believe how long it took me to really grok object-oriented programming. I just didn't get it, until I started thinking of OOP as being just syntax for keeping functions (called methods) close to the data they belong with. There is more to OOP than that, but that was my first step: OOP helps you keep your functions close to the data they work with. In conventional procedural languages, if you had a function that operates on a string, you would write something like this: Struct string = ... # define a string here # later in the file, perhaps many pages later: function upper(some_string): result = make a new string for char in some_string: if char = 'a': add 'A' to result if char = 'b': add 'B' to result ... if char = 'z': add 'Z' to result else add char to result return result (Aside: don't program uppercase like that! There are more efficient ways, and in Python, it is already provided!) So the problem with this is that your data (say, strings) and the functions that operate on your data (say, upper, lower, and many others) can end up being defined far away from each other, which makes editing the code painful. With OOP, the first change is that the syntax is changed to bring the functions (called methods) together with their data: class string: # put code here to define the string data class # now define all the functions that work on strings def upper(self): # code for upper goes here def lower(self): # code for lower goes here # any other string methods go here Then, later, instead of writing: mystring = blah blah blah print upper(mystring) # this doesn't work since upper is a method we have a slightly different syntax: print mystring.upper() # use this instead That's all you need to know to start using object oriented programming in Python! Many operations are implemented as methods, for instance strings have upper and lower methods, lists have append and remove methods, and many more. You'll soon learn the operations like len() that aren't methods, but old-school functions. As I said, there is a lot more to OOP than just making it easier to organise your program files, but that was the realisation that helped me get OOP. The next step is to understand inheritance. Inheritance means that you can create a new class (the subclass) which inherits -- borrows -- data and methods from another class (the super class). Here is a stupid example: class StupidStr(str): # inherit from str def upper(self): return *** This class StupidStr is exactly like the ordinary string, except the upper() method has been replaced to do something trivial and stupid: py s = StupidStr(Hello World) py s.lower() # inherits the behaviour of normal str 'hello world' py s.upper() # overrides the normal upper method for my stupid one '***' Why would you do this? Well, obviously you wouldn't do something so stupid except as an exercise. It's hard to give *simple* real life examples that aren't contrived, but here's one that works for me: Suppose you're writing software to control a model car. You might start off by collecting some basic defaults: class DefaultModelCar: model = Unknown BRAKE_COMMAND = B FORWARD_COMMAND = F REVERSE_COMMAND = R ACCELERATE_COMMAND = A TURN_LEFT_COMMAND = TL TURN_RIGHT_COMMAND = TR def send_command(self, command): # Send a command to the model car. # Put the code here to actually communicate with the car. ... def forward(self): # Drive forward. if self.direction == Reverse: # Brake first, then move forward. self.stop() self.send_command(self.FORWARD_COMMAND) self.send_command(self.ACCELERATE_COMMAND) self.direction = Forward def reverse(self): if self.direction == Forward: self.stop() self.send_command(self.REVERSE_COMMAND) self.send_command(self.ACCELERATE_COMMAND) self.direction = Reverse def stop(self): self.send_command(self.BRAKE_COMMAND) self.direction = Stopped and so on. Now, this default set of commands probably won't work for any actual model car, but at least you can run it and test that it works as you expect: car = DefaultModelCar() # Create a car instance
Re: [Tutor] Beginner question
On 10 Aug 2013, at 04:30, eschneide...@comcast.net wrote:
I've been learning python from the website 'inventwithpython.com', and I'm on
a chapter that covers the following code:
import random
import time
def displayIntro():
print('You are in a land full of dragons. In front of you,')
print('you see two caves. In one cave, the dragon is friendly')
print('and will share his treasure with you. The other dragon')
print('is greedy and hungry, and will eat you on sight.')
print()
def chooseCave():
cave = ''
while cave != '1' and cave != '2':
print('Which cave will you go into? (1 or 2)')
cave = input()
return cave
def checkCave(chosenCave):
print('You approach the cave...')
time.sleep(2)
print('It is dark and spooky...')
time.sleep(2)
print('A large dragon jumps out in front of you! He opens his jaws
and...')
print()
time.sleep(2)
friendlyCave = random.randint(1, 2)
if chosenCave == str(friendlyCave):
print('Gives you his treasure!')
else:
print('Gobbles you down in one bite!')
playAgain = 'yes'
while playAgain == 'yes' or playAgain == 'y':
displayIntro()
caveNumber = chooseCave()
checkCave(caveNumber)
print('Do you want to play again? (yes or no)')
playAgain = input()
I'm confused about what the line 'checkCave(caveNumber)' does and how it
works. I would appreciate any help with this
Thank you,
Eric
Hi Eric,
This line calls the method 'checkCave()'. This method takes the argument
caveNumber (checkCave(caveNumber) , which is a string returned from user input
generated in the method chooseCave().
In checkCave method, the value (caveNumber) is then used in a if/else statement
to compare with a random integer (parsed to a string str(frindlyCave)) to
determine whether you will be eaten or given treasure ;)
Hope that was of some help.
Ciaran
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Re: [Tutor] Beginner question
On 12 August 2013 02:14, Karim Liateni kliat...@gmail.com wrote: 5ÿt5ÿ6hhhyyyfrrtr eschneide...@comcast.net a écrit : I've been learning python from the website 'inventwithpython.com', and I'm on a chapter that covers the following code: Just a quick note - not on the algorithm itself. If you run that in some IDEs, such as Wing101, all the time.sleep()s will concatenate, and all the prints will then print at once with no delay ;') If that happens, run it from the command line or try a different IDE. Jim -- If you don't know it's impossible, it's easier to do. --Neil Gaiman The Process is not the Picture...Reality can only be proved to be weakly-objective. Strong objectivity is a myth. --Bernardo Kastrup You cannot use logic to justify logic, so logic itself has no basis other than faith. --Agrippa ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Beginner question
def checkCave(chosenCave):
print('You approach the cave...')
time.sleep(2)
print('It is dark and spooky...')
time.sleep(2)
print('A large dragon jumps out in front of you! He opens his jaws
and...')
print()
time.sleep(2)
friendlyCave = random.randint(1, 2)
if chosenCave == str(friendlyCave):
print('Gives you his treasure!')
else:
print('Gobbles you down in one bite!')
playAgain = 'yes'
while playAgain == 'yes' or playAgain == 'y':
displayIntro()
caveNumber = chooseCave()
checkCave(caveNumber)
print('Do you want to play again? (yes or no)')
playAgain = input()
Hi,
- Here we are passing the chosen integer (1 or 2) got from chooseCave()
method to checkCave as arguement
- When called in while loop inside checkCave the following happens;
- The statements of approaching the cave and seeing the dragon are
printed with a time interval of 2 secs between each
- Randomly either 1 or 2 is generated by the randint() method of random
module in python.
- That randomly generated integer (1 0r 2) is compared with our integer
input (1 or 2)
- If they match dragon gives us gold. Or else
- We will be eaten by dragon :)
But in the code there is a flaw. input() will evaluate your user input.
i.e. If you give an integer expression it will tell the answer. And when
you provide a number it will take it as int type. See below.
var = input()
1+2+3
var
6
var = input()
2
type(var)
type 'int'
var = input()
s
Traceback (most recent call last):
File stdin, line 1, in module
File string, line 1, in module
NameError: name 's' is not defined
var = input()
So since the integer number is checked with string in Line 13, it will run
into infinite loop. If you use raw_input() instead of input() you will be
able to run the example.
Regards,
Krishnan
On Mon, Aug 12, 2013 at 10:25 PM, Jim Mooney cybervigila...@gmail.comwrote:
On 12 August 2013 02:14, Karim Liateni kliat...@gmail.com wrote:
5ÿt5ÿ6hhhyyyfrrtr
eschneide...@comcast.net a écrit :
I've been learning python from the website 'inventwithpython.com', and
I'm on a chapter that covers the following code:
Just a quick note - not on the algorithm itself. If you run that in some
IDEs, such as Wing101, all the time.sleep()s will concatenate, and all the
prints will then print at once with no delay ;') If that happens, run it
from the command line or try a different IDE.
Jim
--
If you don't know it's impossible, it's easier to do. --Neil Gaiman
The Process is not the Picture...Reality can only be proved to be
weakly-objective. Strong objectivity is a myth. --Bernardo Kastrup
You cannot use logic to justify logic, so logic itself has no basis other
than faith. --Agrippa
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Re: [Tutor] Beginner question
But in the code there is a flaw. input() will evaluate your user input.
i.e. If you give an integer expression it will tell the answer. And when
you provide a number it will take it as int type. See below.
Hi,
Ignore my above statements if using Python 3. Sorry my bad. Had a doubt and
went to the site to see the version of python used. My statement above is
correct only if run in Python 2 and not in 3.
Regards,
Krishnan
On Mon, Aug 12, 2013 at 11:01 PM, Krishnan Shankar
i.am.song...@gmail.comwrote:
def checkCave(chosenCave):
print('You approach the cave...')
time.sleep(2)
print('It is dark and spooky...')
time.sleep(2)
print('A large dragon jumps out in front of you! He opens his jaws
and...')
print()
time.sleep(2)
friendlyCave = random.randint(1, 2)
if chosenCave == str(friendlyCave):
print('Gives you his treasure!')
else:
print('Gobbles you down in one bite!')
playAgain = 'yes'
while playAgain == 'yes' or playAgain == 'y':
displayIntro()
caveNumber = chooseCave()
checkCave(caveNumber)
print('Do you want to play again? (yes or no)')
playAgain = input()
Hi,
- Here we are passing the chosen integer (1 or 2) got from chooseCave()
method to checkCave as arguement
- When called in while loop inside checkCave the following happens;
- The statements of approaching the cave and seeing the dragon are
printed with a time interval of 2 secs between each
- Randomly either 1 or 2 is generated by the randint() method of
random module in python.
- That randomly generated integer (1 0r 2) is compared with our
integer input (1 or 2)
- If they match dragon gives us gold. Or else
- We will be eaten by dragon :)
But in the code there is a flaw. input() will evaluate your user input.
i.e. If you give an integer expression it will tell the answer. And when
you provide a number it will take it as int type. See below.
var = input()
1+2+3
var
6
var = input()
2
type(var)
type 'int'
var = input()
s
Traceback (most recent call last):
File stdin, line 1, in module
File string, line 1, in module
NameError: name 's' is not defined
var = input()
So since the integer number is checked with string in Line 13, it will run
into infinite loop. If you use raw_input() instead of input() you will be
able to run the example.
Regards,
Krishnan
On Mon, Aug 12, 2013 at 10:25 PM, Jim Mooney cybervigila...@gmail.comwrote:
On 12 August 2013 02:14, Karim Liateni kliat...@gmail.com wrote:
5ÿt5ÿ6hhhyyyfrrtr
eschneide...@comcast.net a écrit :
I've been learning python from the website 'inventwithpython.com', and
I'm on a chapter that covers the following code:
Just a quick note - not on the algorithm itself. If you run that in some
IDEs, such as Wing101, all the time.sleep()s will concatenate, and all the
prints will then print at once with no delay ;') If that happens, run it
from the command line or try a different IDE.
Jim
--
If you don't know it's impossible, it's easier to do. --Neil Gaiman
The Process is not the Picture...Reality can only be proved to be
weakly-objective. Strong objectivity is a myth. --Bernardo Kastrup
You cannot use logic to justify logic, so logic itself has no basis
other than faith. --Agrippa
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[Tutor] Beginner question
I've been learning python from the website 'inventwithpython.com', and I'm on a
chapter that covers the following code:
import random
import time
def displayIntro():
print('You are in a land full of dragons. In front of you,')
print('you see two caves. In one cave, the dragon is friendly')
print('and will share his treasure with you. The other dragon')
print('is greedy and hungry, and will eat you on sight.')
print()
def chooseCave():
cave = ''
while cave != '1' and cave != '2':
print('Which cave will you go into? (1 or 2)')
cave = input()
return cave
def checkCave(chosenCave):
print('You approach the cave...')
time.sleep(2)
print('It is dark and spooky...')
time.sleep(2)
print('A large dragon jumps out in front of you! He opens his jaws and...')
print()
time.sleep(2)
friendlyCave = random.randint(1, 2)
if chosenCave == str(friendlyCave):
print('Gives you his treasure!')
else:
print('Gobbles you down in one bite!')
playAgain = 'yes'
while playAgain == 'yes' or playAgain == 'y':
displayIntro()
caveNumber = chooseCave()
checkCave(caveNumber)
print('Do you want to play again? (yes or no)')
playAgain = input()
I'm confused about what the line 'checkCave(caveNumber)' does and how it works.
I would appreciate any help with this
Thank you,
Eric
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Re: [Tutor] Beginner question
On 10/08/13 04:30, eschneide...@comcast.net wrote:
I've been learning python from the website 'inventwithpython.com', and
I'm on a chapter that covers the following code:
import random
import time
def displayIntro():
print('You are in a land full of dragons. In front of you,')
print('you see two caves. In one cave, the dragon is friendly')
print('and will share his treasure with you. The other dragon')
print('is greedy and hungry, and will eat you on sight.')
print()
def chooseCave():
cave = ''
while cave != '1' and cave != '2':
print('Which cave will you go into? (1 or 2)')
cave = input()
return cave
def checkCave(chosenCave):
print('You approach the cave...')
time.sleep(2)
print('It is dark and spooky...')
time.sleep(2)
print('A large dragon jumps out in front of you! He opens his jaws
and...')
print()
time.sleep(2)
friendlyCave = random.randint(1, 2)
if chosenCave == str(friendlyCave):
print('Gives you his treasure!')
else:
print('Gobbles you down in one bite!')
playAgain = 'yes'
while playAgain == 'yes' or playAgain == 'y':
displayIntro()
caveNumber = chooseCave()
checkCave(caveNumber)
print('Do you want to play again? (yes or no)')
playAgain = input()
I'm confused about what the line 'checkCave(caveNumber)' does and how it
works. I would appreciate any help with this
It calls the checkCave function defined above. It passes in the cave
'number' as an argument. The function basically decides whether the
monster inside is friendly or not and prints an appropriate message.
It then returns control to the main while loop.
Does that help?
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
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[Tutor] beginner question
When writing a simple for loop like so: for x in f where f is the name of a file object, how does Python know to interpret the variable x as a line of text, rather than,say, an individual character in the file? Does it automatically treat text files as sequences of lines? -- Mayo Adams 287 Erwin Rd. Chapel Hill, NC 27514 (919)-968-7889 mayoad...@gmail.com ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] beginner question
On 01-Nov-11 08:34, Mayo Adams wrote: When writing a simple for loop like so: for x in f where f is the name of a file object, how does Python know to interpret the variable x as a line of text, rather than,say, an individual character in the file? Does it automatically treat text files as sequences of lines? Every object defines what its behavior will be when asked to do something. In this case, file objects know that they are capable of iterating over a list of their contents by being used in a for x in f loop construct. The file object knows to respond to that by yielding up a line from the file for every iteration. You could, theoretically, write a variation of the file object class which iterated over characters, or logical blocks (records of some sort) within files, and so forth. -- Steve Willoughby / st...@alchemy.com A ship in harbor is safe, but that is not what ships are built for. PGP Fingerprint 4615 3CCE 0F29 AE6C 8FF4 CA01 73FE 997A 765D 696C ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] beginner question
Steve Willoughby wrote: On 01-Nov-11 08:34, Mayo Adams wrote: When writing a simple for loop like so: for x in f where f is the name of a file object, how does Python know to interpret the variable x as a line of text, rather than,say, an individual character in the file? Does it automatically treat text files as sequences of lines? Every object defines what its behavior will be when asked to do something. In this case, file objects know that they are capable of iterating over a list of their contents by being used in a for x in f loop construct. The file object knows to respond to that by yielding up a line from the file for every iteration. You could, theoretically, write a variation of the file object class which iterated over characters, or logical blocks (records of some sort) within files, and so forth. Here's a simple example of a class derived from file that iterates over characters (bytes) instead of lines. Standard file: for line in open(tmp.txt): ... print repr(line) ... 'this\n' 'is but an\n' 'example\n' Modified file class: class MyFile(file): ... def next(self): ... c = self.read(1) ... if not c: ... raise StopIteration ... return c ... for c in MyFile(tmp.txt): ... print repr(c) ... 't' 'h' 'i' 's' '\n' 'i' 's' ' ' 'b' 'u' 't' ' ' 'a' 'n' '\n' 'e' 'x' 'a' 'm' 'p' 'l' 'e' '\n' ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] beginner question
Mayo Adams wrote:
When writing a simple for loop like so:
for x in f
where f is the name of a file object, how does Python know to interpret
the variable x as a line of text, rather than,say, an individual character
in the file? Does it automatically
treat text files as sequences of lines?
Nice question! But the answer is a little bit complicated. The short
answer is:
File objects themselves are programmed to iterate line by line rather
than character by character. That is a design choice made by the
developers of Python, and it could have been different, but this choice
was made because it is the most useful.
The long answer requires explaining how for-loops work. When you say
for x in THINGY: ...
Python first asks THINGY to convert itself into a iterator. It does that
by calling the special method THINGY.__iter__(), which is expected to
return an iterator object (which may or may not be THINGY itself). If
there is no __iter__ method, then Python falls back on an older sequence
protocol which isn't relevant to files. If that too fails, then Python
raises an error.
So what's an iterator object? An iterator object must have a method
called next (in Python 2), or __next__ (in Python 3), which returns
the next item. The object is responsible for knowing what value to
return each time next() is called. Python doesn't need to know anything
about the internal details of the iterator, all it cares about is that
when it calls THINGY.next() or THINGY.__next__(), the next item will be
returned. All the intelligence is inside the object, not in Python.
When there are no more items left to return, next() should raise
StopIteration, which the for loop detects and treats as loop is now
finished rather than as an error.
So, the end result of all this is that Python doesn't care what THINGY
is, so long as it obeys the protocol. So anyone can create new kinds of
data that can be iterated over. In the case of files, somebody has
already done that for you: files are built into Python.
Built-in file objects, like you get from f = open(some file, r),
obey the iterator protocol. We can run over it by hand, doing exactly
what Python does in a for-loop, only less conveniently.
Suppose we have a file containing fee fi fo fum split over four lines.
Now let's iterate over it by hand. File objects are already iterators,
so in Python 3 they have their own __next__ method and there's no need
to call __iter__ first:
f = open('temp.txt', 'r')
f.__next__()
'fee\n'
f.__next__()
'fi\n'
f.__next__()
'fo\n'
f.__next__()
'fum\n'
f.__next__()
Traceback (most recent call last):
File stdin, line 1, in module
StopIteration
So the file object itself keeps track of how much of the file has been
read, and the Python interpreter doesn't need to know anything about
files. It just needs to know that the file object is iterable. I already
know this, so I took a short-cut, calling f.__next__() directly. But
Python doesn't know that, it performs one extra step: it calls
f.__iter__ to get an iterator object:
f.__iter__()
_io.TextIOWrapper name='temp.txt' encoding='UTF-8'
In this case, that iterator object is f itself, and now the Python
interpreter goes on to call __next__() repeatedly.
File objects are actually written in C for speed, but if they were
written in pure Python, they might look something vaguely like this:
class File(object):
def __init__(self, name, mode='r'):
self.name = name
if mode == 'r':
... # open the file in Read mode
elif mode == 'w':
... # open in Write mode
else:
# actually there are other modes too
raise ValueError('bad mode')
def __iter__(self):
return self # I am my own iterator.
def read(self, n=1):
# Read n characters. All the hard work is in here.
...
def readline(self):
# Read a line, up to and including linefeed.
buffer = []
c = self.read()
buffer.append(c)
while c != '' and c != '\n':
c = self.read() # Read one more character.
buffer.append(c)
return ''.join(buffer)
def __next__(self):
line = self.readline()
if line == '':
# End of File
raise StopIteration
else:
return line
--
Steven
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Re: [Tutor] Beginner question(s)
* Ismael Garrido [EMAIL PROTECTED] [2006-06-18 19:34]: Alan Gauld wrote: Also, does anyone know of a PDA that would run python? There was a project called pippy, but I haven't heard anything of it recently so I don't know if its still around or if it runs on modern PDAs - I think it was PalmOS anyhow... Pippy is quite dead. No development done recently. It supposedly runs fine, but runs only Python 1.5. Last I used it, it worked fine, but it was limited. -- David Rock [EMAIL PROTECTED] ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] Beginner question(s)
Hi, Im working through Python Programming for the Absolute Beginner. One of the challenges at the end of chapter 4 is to get a message from the user and then print it out backwards. I have message = raw_input(Enter your message:) count = len(message) print count which gives me the number of characters in the message. I tried to use a for loop: for i in range(len(message)-1,-1, -1): print i, but I just get the numeric values of the string. Can anyone help? Also, does anyone know of a PDA that would run python? TIA ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Beginner question(s)
message = raw_input(Enter your message:) for i in range(len(message)-1,-1, -1): print i, but I just get the numeric values of the string. Can anyone help? As an alternative approach consider converting to a list and using the reverse method... Also, does anyone know of a PDA that would run python? There was a project called pippy, but I haven't heard anything of it recently so I don't know if its still around or if it runs on modern PDAs - I think it was PalmOS anyhow... There was rumours of a Pocket Windows version too but I've never really been interested in that one... Alan G. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Beginner question(s)
Alan Gauld wrote: Also, does anyone know of a PDA that would run python? There was a project called pippy, but I haven't heard anything of it recently so I don't know if its still around or if it runs on modern PDAs - I think it was PalmOS anyhow... Pippy is quite dead. No development done recently. It supposedly runs fine, but runs only Python 1.5. If you want it, it's at: http://sourceforge.net/projects/pippy Ismael ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Beginner Question
On 6/18/06, Josh F [EMAIL PROTECTED] wrote: re. Beginner QuestionI'm still in the fairly early stages of learning Python, but I have anintermediate level of HTML, CSS, and VB6 knowledge along with thefundamentals of C and C++ and a very little bit of PERL.. But enough about me...Here's the solution.message = raw_input(Enter your message:)print message[-1::-1]just another noob here.but wouldn't his way work like this: message = foobarfor i in range(len(message)-1,-1,-1):... print message[i],...r a b o o fi guess there's lots of ways to do it. that's my 2 cents. Slicing a string takes three arguments, all of which are optional: The firstcharacter to be sliced, the last character to be sliced, and tio slice every nth character.In Python strings, -1 refers to the last character in the string and thusbecomes the first argument.You don't specify the second argument because you're printing the stringfrom end to beginning. Finallly, the -1 in the 3rd argument indicates that you want the string tobe printed in reverse order (i.e. iterate backwards by one character).Message: 1Date: Sun, 18 Jun 2006 05:58:38 -0500 From: Bill Tatum [EMAIL PROTECTED]Subject: [Tutor] Beginner question(s)To: tutor@python.orgMessage-ID: [EMAIL PROTECTED]Content-Type: text/plain; charset=us-asciiHi,I'm working through Python Programming for the Absolute Beginner.One of the challenges at the end of chapter 4 is to get a message from the userandthen print it out backwards. I have.message = raw_input(Enter your message:) count = len(message)print countwhich gives me the number of characters in the message.I tried to use afor loop:for i in range(len(message)-1,-1, -1): print i,but I just get the numeric values of the string.Can anyone help?Also, does anyone know of a PDA that would run python? TIA___Tutor maillist-Tutor@python.org http://mail.python.org/mailman/listinfo/tutor-- Daniel McQuay[EMAIL PROTECTED] boxster.homelinux.orgH: 814.825.0847M: 814-341-6233 ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Beginner question(s)
Also, does anyone know of a PDA that would run python? Some of the new Nokias run python: http://www.forum.nokia.com/python -- John. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Beginner question (variables, namespaces...) (fwd)
From: Jesse [EMAIL PROTECTED] I tried redefining the higher-order variables as functions, but it didn't quite work. Here's a simplified example: var1 = 2 def timestwo(x): return x*2 var2 = timestwo(var1) print var1, var2 var1 = 3 print var1, var2 This results in the output: 2, 4 3,4 You still have to call the function whenever you need the value. print var1, timestwo(var1) var1 = 3 print var1, timestwo(var1) ..which is not what I'm aiming for. Maybe I'll have to follow Bob's advice and just store all of the variable assignments in a function, and then call the function every time I change one of the variables (based on user input). I could still leave the higher-order variables as functions as per your advice, but that alone doesn't seem to do the trick. Unless I've missed something. Danny's suggestion of using class properties is a good one, it allows you to automate the recalculation of the variables, and also protect against directly assigning one of the calculated values. Here is a class that has two attributes, val and val2. val can be assigned normally. val2 is read-only and always equal to twice val. Whenever a new value is assigned to val, the internal _recalculate() method is called. This is slightly more complex than needed for this example (_set_val()) could calculate val2 directly) but it extends easily to multiple settable and calculated values. The only problem with this approach is that it is not really beginner material, you need some understanding of classes and properties. I don't know of any beginner references for properties but you could try this: http://users.rcn.com/python/download/Descriptor.htm#properties Anyway here is the code: # class AutoCompute(object): def __init__(self, val): self.val = val # Create a property named val # Setting val triggers recomputation def _set_val(self, val): self._val = val self._recompute() def _get_val(self): return self._val val = property(_get_val, _set_val) # Create a read-only property named val2 def _get_val2(self): return self._val2 val2 = property(_get_val2) def _recompute(self): self._val2 = self._val * 2 ac = AutoCompute(3) print ac.val, ac.val2 # Assigning to ac.val changes ac.val2 also ac.val = 4 print ac.val, ac.val2 # This raises AttributeError, val2 is read-only ac.val2 = 5 ### When run, the output is 3 6 4 8 Traceback (most recent call last): File F:\Tutor\ComputedProperty.py, line 33, in ? ac.val2 = 5 AttributeError: can't set attribute ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Beginner question (variables, namespaces...) (fwd)
I tried redefining the higher-order variables as functions, but it didn't quite work. Here's a simplified example: var1 = 2 def timestwo(x): return x*2 var2 = timestwo(var1) print var1, var2 var1 = 3 print var1, var2 Try: ## print 2, timestwo(2) print 3, timestwo(3) ## Alternatively, try: ## var1 = 2 print var1, timestwo(var1) var1 = 3 print var1, timestwo(var1) ## What do you expect to see? ..which is not what I'm aiming for. Maybe I'll have to follow Bob's advice and just store all of the variable assignments in a function, and then call the function every time I change one of the variables (based on user input). I could still leave the higher-order variables as functions as per your advice, but that alone doesn't seem to do the trick. Unless I've missed something. You're missing something. *wink* Play with this a little more. It's something basic in Python, and you'll want to get this squared away so it doesn't cause you grief later. The model you have about how variables behave in Python is slightly off still: I think you're still thinking of them like math equations. But Python's model for assigning variable names to values don't work like equality: it's more of a this box now contains the value described by the right hand side at this particular time. So if we see: a = 3 b = 4 a = a + b we can model this as: [a : 3] (after stmt: a = 3) [a : 3, b : 4] (after stmt: b = 4) [a : 7, b : 4](after stmt: a = a + b) where we keep a list of names and their current values. (I'm just using an ad-hoc notation for the stuff in the brackets.) Assignment erases the old value and replaces it with a new one as we flow through our program. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Beginner question (variables, namespaces...) (fwd)
..which is not what I'm aiming for. Maybe I'll have to follow Bob's advice and just store all of the variable assignments in a function, and then call the function every time I change one of the variables (based on user input). I could still leave the higher-order variables as functions as per your advice, but that alone doesn't seem to do the trick. Unless I've missed something. Danny's suggestion of using class properties is a good one, it allows you to automate the recalculation of the variables, and also protect against directly assigning one of the calculated values. Just wanted to clarify that this is not my suggestion: Alan proposed this. But I think we should steer away a little away from full-fledged classes at the moment. The professional solution would be to do this, but I'm not sure how appropriate it is for Jesse to do this yet. Jesse is still confused about how variables work. In which case, suggesting him to look at classes will just make things worse. *grin* ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] Beginner question (variables, namespaces...)
Why is it that when one variable is assigned a value in terms of another variable, assigning a new value to the first doesn't change the value of the second? This is giving me a huge headache, since I have a bunch of variables defined in terms of one another, and I want to be able to dynamically update them (I did not include the definitions of the functions overstock and roundup, but they work): stock = float(raw_input(Enter stock (in terms of portions: ))container = float(raw_input(Enter portions percontainer: ))price_per_container = float(raw_input(Enter price per container: )) weekly_quota = float(raw_input(Enter quota (in terms of portions): ))extra = overstock(stock, weekly_quota) # overstock returns 0 if the first argument is less than the second; otherwise itreturns the difference between the first argument and the second.need = weekly_quota - extrabuy_containers = roundup(need/container) # roundup rounds a non-integer to the next highest integer buy_portions = buy_containers * containerleftover = buy_portions - needcost = price_per_container * buy_containers I would like to write a function that will update the values of the above variables given an increase inonly thestock variable. Otherwise I'd have to repeat a bunch of code...:( Jesse ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Beginner question (variables, namespaces...)
On Fri, 7 Apr 2006, Jesse wrote: Why is it that when one variable is assigned a value in terms of another variable, assigning a new value to the first doesn't change the value of the second? Hi Jesse, If you have a variable that depends on the values of other parameters, that's just begging to be represented as a function. Let's look at some of those computations: stock = float(raw_input(Enter stock (in terms of portions: )) container = float(raw_input(Enter portions per container: )) price_per_container = float(raw_input(Enter price per container: )) weekly_quota = float(raw_input(Enter quota (in terms of portions): )) extra = overstock(stock, weekly_quota) need = weekly_quota - extra buy_containers = roundup(need/container) # roundup rounds a non-integer to the next highest integer buy_portions = buy_containers * container leftover = buy_portions - need cost = price_per_container * buy_containers Yeah, rather than code these as explicit variables, I'd strongly recommend rewriting each of these as functions. Concretely: def extra(stock, weekly_quota): return overstock(stock, weekly_quota) def need(stock, weekly_quota): return weekly_quota - extra(stock, weekly_quota) def buy_containers(stock, weekly_quota, container): return roundup(need(stock, weekly_quota) - extra(stock, weekly_quota)) ... It's a little ugly, but this coding explicitely defines the dependencies between the inputs into our system and the expected outputs. When we look at buy_containers(), we can easily see that any change in the stock, weekly_quote, or container parameters may have some profound affect on the output to buy_containers(). That dependency between input and output is what we try to capture when we write a function. So if you recode your assignment statements as function definitions, you should be better able to handle changes to your input. If we think of the names we use for these concepts, there's something ironic that functions behave better on varying data than variables. Oh well. As an advanced aside: the equations that you're writing into Python, unfortunately, aren't treated as real math equations, but as separate, independent assignment statements. I think I know what you want, but Python doesn't provide it out of the box. What I think you want is called constraint programming. Such systems do exist. For example: http://www.logilab.org/projects/constraint I can't vouch for the maturity of logilab's constraint module; I haven't played with it yet. But if you're interested, you may want to look at the treatment of simple constraint systems in the classic textbook Structure and Interpretation of Computer Programs: http://mitpress.mit.edu/sicp/full-text/book/book-Z-H-22.html#%_sec_3.3.5 It should be very possible to adapt the material there into Python, although it might take a fair bit of work if you're not familiar with Scheme. Good luck to you! ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Beginner question (variables, namespaces...)
Jesse wrote: Why is it that when one variable is assigned a value in terms of another variable, assigning a new value to the first doesn't change the value of the second? This is giving me a huge headache, since I have a bunch of variables defined in terms of one another, and I want to be able to dynamically update them (I did not include the definitions of the functions overstock and roundup, but they work): stock = float(raw_input(Enter stock (in terms of portions: )) container = float(raw_input(Enter portions per container: )) price_per_container = float(raw_input(Enter price per container: )) weekly_quota = float(raw_input(Enter quota (in terms of portions): )) extra = overstock(stock, weekly_quota) # overstock returns 0 if the first argument is less than the second; otherwise it returns the difference between the first argument and the second. need = weekly_quota - extra buy_containers = roundup(need/container) # roundup rounds a non-integer to the next highest integer buy_portions = buy_containers * container leftover = buy_portions - need cost = price_per_container * buy_containers I would like to write a function that will update the values of the above variables given an increase in only the stock variable. Otherwise I'd have to repeat a bunch of code...:( def recalculate(): global extra, need, buy_containers, buy_portions, leftover, cost extra = overstock(stock, weekly_quota) need = weekly_quota - extra buy_containers = roundup(need/container) buy_portions = buy_containers * container leftover = buy_portions - need cost = price_per_container * buy_containers That's all there is to it. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Beginner question (variables, namespaces...) (fwd)
-- Forwarded message -- Date: Fri, 7 Apr 2006 21:05:33 -0600 From: Jesse [EMAIL PROTECTED] To: Danny Yoo [EMAIL PROTECTED] Subject: Re: [Tutor] Beginner question (variables, namespaces...) I tried redefining the higher-order variables as functions, but it didn't quite work. Here's a simplified example: var1 = 2 def timestwo(x): return x*2 var2 = timestwo(var1) print var1, var2 var1 = 3 print var1, var2 This results in the output: 2, 4 3,4 ..which is not what I'm aiming for. Maybe I'll have to follow Bob's advice and just store all of the variable assignments in a function, and then call the function every time I change one of the variables (based on user input). I could still leave the higher-order variables as functions as per your advice, but that alone doesn't seem to do the trick. Unless I've missed something. Jesse ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
