from:"steve"


On 12-Jun-2013, at 05:48, Manigopal Vepati manigopa...@gmail.com wrote:

 Hi,
 
 I need scripts for the following .
 
 1) check whether username and password fields are present in Gmail
 2) Code to access the system which doesn’t have ip address
 

And what have you found as you've started writing those scripts? Anything in 
particular you've run into that you're puzzled by?

This list can be a wonderful resource to assist you as you learn to write your 
first scripts, but please remember that it is staffed by volunteers who take 
their valuable personal time to help others learn. We're not here to perform 
contract programming for you, or to do homework for you, just to help you along 
the way as you learn to program in Python.

When you do get to a point where you need help, you need to be sure to ask 
meaningful questions and provide as much background information as would be 
needed for someone to truly understand what you're doing.  For example, in the 
message you sent, it's impossible to know what you're even trying to accomplish 
because you don't say what you mean by fields present in Gmail (I can think 
of a dozen completely different things that could mean, and you don't give 
enough information to actually be able to move forward with any of them even 
were I to guess which of them you intended.  I can't even make sense of the 
second one at all. You don't say what kind of access you're referring to, or 
what IP address has to do with anything (e.g., are you asking how to look up an 
IP address in DNS, or that the system isn't on a standard network which uses IP 
protocols, or what).

Assuming that you have your programming goals better developed than is apparent 
in your email, make a good start at your implementation and then tell us in 
detail what  you get stuck with. 

And just because we tend to get asked this from time to time, in case what you 
mean here is to somehow hack or illegally access a system you aren't 
otherwise allowed to access, we won't help you at all with anything like that. 
Don't bother even asking.

 
 i am using python 3.3

Ok, that's a very valuable piece of information. Since you're also accessing 
resources outside your scripts (other machines and mail services), it would 
also be useful to know the operating system and version of the systems involved.

 
 thanks
 manigopal
 ___
 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] Hi, First question


On 16-Jun-2013, at 09:21, Mark Lawrence breamore...@yahoo.co.uk wrote:

 On 16/06/2013 16:55, Chris “Kwpolska” Warrick wrote:
 On Sat, Jun 15, 2013 at 7:22 AM, Patrick Williams pdw0...@gmail.com wrote:
 Hi so I am making a bit of code to extract a bit of numbers data from a file
 and then find the average of that data, however while I can get the code to
 extract each specific piece of data I need, I can't seem to get the numbers
 to add separately  so I can get a proper average. My sum1 variable seems to
 only take the last bit of data entered. I was just wondering if anyone knows
 what I'm doing wrong, the course I'm following hadn't started using regex
 (or even proper lists) at this point, so there must be a way to do it
 without. here's the code. the average of the data should be 0.6789 or
 something, but I get 0.0334343 or something.
 
 count=0
 lst=list()
 
 `lst = []` is the preferred syntax.
 
 fname='mbox-short.txt'
 fhand=open(fname)
 for line in fhand:
 if line.startswith('X-DSPAM-Confidence:'):
 count=count+1
 colpos=line.find(':')
 zpos=line.find('0',colpos)
 num=float(line[zpos:50])
 sum1=0+num
 avg=float(sum1)/int(count)
 
 I'll assume unless someone tells me differently that sum1 does not need 
 reinitialising every time, and that avg needs to be calculated when the loop 
 has finished.
 
 print 'Count-', count,'--', 'Average-', avg
 
 Any help at all is appreciated, and thanks in advance.
 
 
 I don’t know what file you used, but the message you sent got this
 header from Gmail, and the format doesn’t seem to be much different:
 
 X-Spam-Evidence: '*H*': 0.79; '*S*': 0.00; 'separately': 0.09;
'wrong,': 0.09; 'subject:question': 0.10; 'code.': 0.18;
'variable': 0.18; 'bit': 0.19; 'advance.': 0.19; 'seems': 0.21;
'8bit%:5': 0.22; 'print': 0.22; 'skip:l 30': 0.24; '\xa0so': 0.24;
 [snip 11 more lines]
 (replaced tabstops with spaces)
 
 Can you guess what’s wrong in your code?
 
 You are reading only the first line. 
 
 What does for line in fhand: do then?

I think what that was referring to was the assumption that you're reading mail 
header lines from that file, and they can be split out over multiple lines (see 
the example cited above).  If that's the case, then for line in fhand will 
iterate over each line in the file, but you're only looking for lines which 
start with X-Spam-.. which would only be the FIRST part of the header if it's 
split out like that.

If your file is NOT organized like that, then your situation is different.  
However, if your files are like that, you're going to randomly miss data if the 
fields you're looking for don't happen to be on the first line of the 
multi-line header.

Now if you are reading RFC-822 (et al) standard mail messages in those files, 
there are bits of the Python standard library which will be immensely useful to 
you in parsing out those headers rather than trying to do it yourself.  That's 
something you're going to find to be the case frequently with Python.
 
 
 -- 
 Steve is going for the pink ball - and for those of you who are watching in 
 black and white, the pink is next to the green. Snooker commentator 
 'Whispering' Ted Lowe.
 
 Mark Lawrence
 
 ___
 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] Is there a programmatic use for keys() and values()


On 16-Jun-2013, at 10:49, Jim Mooney cybervigila...@gmail.com wrote:

 On 16 June 2013 01:43, Roel Schroeven r...@roelschroeven.net wrote:
 
 Can't you disable that behavior somewhere in the settings of your IDE? I
 know IDEs do that to be helpful, but I don't like it and so far I've been
 able to disable it in all IDEs I've used.
 
 
 VIM sounds good but I don't think there's a version for Windows.

There's a version of VIM for about everything, including Windows and OS X.

 As for the one-week learning curve on VIM, reminds me of that claim
 for Joomla. Yes, you can set up a site in a few hours after your first
 install of Joomla, but learning to fix the blowups and problems while
 people are screaming at you, since it's all public, takes considerably
 longer. Although an editor that's been around since the stone age
 probably doesn't blow up. I doubt VIM has a constant stream of
 upgrades (not always compatible), bug fixes, and security fixes ;')

Yeah, at this point it's pretty stable.
___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] Is there a programmatic use for keys() and values()


On 16-Jun-2013, at 11:35, Steven D'Aprano st...@pearwood.info wrote:

 On 17/06/13 03:59, Steve Willoughby wrote:
 
 On 16-Jun-2013, at 10:49, Jim Mooney cybervigila...@gmail.com wrote:
 
 On 16 June 2013 01:43, Roel Schroeven r...@roelschroeven.net wrote:
 
 Can't you disable that behavior somewhere in the settings of your IDE? I
 know IDEs do that to be helpful, but I don't like it and so far I've been
 able to disable it in all IDEs I've used.
 
 
 VIM sounds good but I don't think there's a version for Windows.
 
 There's a version of VIM for about everything, including Windows and OS X.
 
 Pfft! VIM. VIM is not the standard editor. There is only one standard editor, 
 ed. That's why it's called an EDitor, not a VIMitor.


Pfft. Only for people who can't handle using the Real One True Editor: TECO.

http://en.wikipedia.org/wiki/TECO_(text_editor)

steve


Although I admit back in my MSDOS days I found a copy of ED which was ported 
there since it was at least infinitely better than EDLIN.
And to be fair, VIM grew out of the classic vi which itself grew directly out 
of ed, so there's a little ed hiding in VIM trying to escape.

___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] Value Error

2013-06-12 Thread Steve Willoughby

or if you try to take the square root of a negative number, etc.

On 12-Jun-2013, at 14:06, Sander Sweers sander.swe...@gmail.com wrote:

 On 06/12/2013 10:49 PM, Jim Mooney wrote:
 Raised when a built-in operation or function receives an argument that has
 the right type but an inappropriate value, and the situation is not
 described by a more precise exception such as
 IndexErrorhttp://docs.python.org/2/library/exceptions.html#exceptions.IndexError
 
 You get this when the function gets the right object but the value of
 that object is not correct. For example int() will attempt to create an
 integer object from a string object. However if that string is not a
 number represented as a sting you run into a ValueError.
 
 int('test')
 
 Traceback (most recent call last):
  File pyshell#0, line 1, in module
int('test')
 ValueError: invalid literal for int() with base 10: 'test'
 
 When we give it the string representation of 123 int() will convert the
 string to an integer.
 
 int('123')
 123
 
 ~Sander
 ___
 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] Value Error

2013-06-12 Thread Steve Willoughby

int('blah') is not a type error because the int() function is expecting to be 
given a string, and it was given a string. The 'blah' is of the correct type.
The problem is that int() couldn't do anything useful with the value of that 
string.

Steve

On 12-Jun-2013, at 14:41, Jim Mooney cybervigila...@gmail.com wrote:

 Dave Angel da...@davea.name
 
import math
 print math.sqrt(-1)
 
 Ah, that's what I was looking for. I already saw it trip on type mismatches 
 like int('blah'). I was looking for what would be an actual inappropriate 
 value that was still the right type.  Although I'm not sure why int('blah') 
 wouldn't be a type error rather than a value error.
 
 Jim 
 
 
 ___
 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] why can you swap an immutable tuple?

2013-05-25 Thread Steve Willoughby


On 2013-5月-25, at 上午11:56, Jim Mooney wrote:

 I thought tuples were immutable but it seems you can swap them, so I'm 
 confused:
 
 a,b = 5,8
 


I think you're confusing mutating the tuples with assigning the immutable 
tuples different names.  The variable names are just labels you attach to them. 
 The tuple values themselves cannot change.  

That said, your example here isn't a tuple but a pair of singleton values. 

If you said 
tuple1 = 1,2,3,4
tuple2 = 5,6,7,8

you create two tuples which are, yes, immutable.  They happen to be called 
tuple1 and tuple2 but that's beside the point of immutability.  If you pass 
them to a function, they'll be known locally there under different names but 
they're still immutable tuples.

Does that help?
--steve
___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] following on

2013-02-18 Thread Steve Willoughby

On Mon, Feb 18, 2013 at 07:01:02PM +, Matthew Ngaha wrote:
  understanding of how everything works.
 
  Use it., Experiment with it. Break it.
  Thats the best way. Read the source code its all available in
  Python or C.
 
 
 Hey can you please tell me which source code youre referring too? The
 initial files that come with Python? also the C code, where can i
 locate this? is C something worth learning? why is Python code
 available in C?

C is definitely worth learning.  So is LISP.  And a handful of other
languages we could enumerate.  It's worth learning if it adds something
useful to your understanding of how computers operate on the instructions you
give them, or if it changes your approach to creating software in a fundamental
way.  Actually using those languages in daily life is not the point.

C, however, is still very useful in a number of situations.  Python programmers
can get leverage from its strengths by--for example--writing 
performance-critical
modules in C and then calling them from their Python programs.

Python itself (well, the standard implementation of it anyway) is written in C.
It has to be written in something that ultimately compiles down to the machine
language which the computer actually uses.  That C code interprets your Python
code so you have a much nicer, high-level programming environment to work with.
But the computer itself doesn't directly understand Python.

 yes i will try not to reinvent the wheel, a lot of tutorials ive read
 seem to always point this out. Just out of curiousity what is a bag,
 stack or circular list? what is needed to create something like this?
 i sort of heard about a stack its a C/C++ thing i think?

None of these are C/C++ things.  They are basic building-blocks of Computer
Science and data structures you'll use regardless of language.  I'd really
recommend investing some time reading up on these and other fundamental
data structures.
-- 
Steve Willoughby|  Using billion-dollar satellites
st...@alchemy.com   |  to hunt for Tupperware.
___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] if/else option for making a choice

2013-02-18 Thread Steve Willoughby

On Mon, Feb 18, 2013 at 07:22:54PM +0100, Niclas Rautenhaus wrote:
 Hello folks,
 I hope it is clear where my problem is.

Not completely, but let's take a look at what you have so far.

 # Set variables for additional items
 Leather = (500)
 int (Leather)
 Clima = (1500)
 int (Clima)
...

You don't need to put parens around the values, but more importantly
note that the int lines don't do anything here.  When you say:

 Hifi = (250)
 int (Hifi)

You set Hifi to the value 250 in the first line, which is fine, but
then you call int() to turn the integer 250 into the integer 250, and
then promptly discard that value.  If you had, for example, a string
250 and wanted to turn it into an integer, you could do something
like

Hifi = int(250)

But simply saying

int(250)

accomplishes nothing.  Do you see why?

 print \n\nPlease enter the basic price: 
 
 basic = int (raw_input())

I'm curious why the price of the car has to be an integer.
Couldn't it be something like 15999.95?

 # Tax is a percentage of the basic car price
 
 Tax = basic * 5 / 100

You would be better off using floats here if you want a real number
as the answer.  You're working in integers.

 int (Tax)

Or maybe you really want integers only to keep the numbers easier
or something.  Fair enough, but again this line does absolutely
nothing.  You truncate Tax to an integer but then discard that integer
value as soon as it's created.

 print \nAdded items:
 # Here the user should have the possibility to pick either yes or no
 print \n\nLeather,(Leather)

The parentheses are unnecessary here.

To have them choose, you need some kind of if statement.  Maybe something
like

choice = raw_input(Would you like windows?)
if choice == 'yes':
windows = 150

There are certainly more sophisticated ways to do this as well, when you get
past the basics of how conditionals (if statements) work.  For example, making
a function that asks each question and handles all the different ways the user
might answer other than typing precisely yes.  Or putting the choices in a
list instead of repeating the choice-asking code over and over.

-- 
Steve Willoughby|  Using billion-dollar satellites
st...@alchemy.com   |  to hunt for Tupperware.
___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] Python Question

2013-01-09 Thread Steve Willoughby


On 2013-1月-7, at 下午3:31, Dylan Kaufman wrote:

 Greetings,
 
 I take Computer Science in school and for a Python program, I have:
 
 from winsound import Beep
 

The first thing I notice is from winsound import …  Could that be a WINDOWS 
library which might not work on a Macintosh?

 Beep(196, 1500)#G
 Beep(262, 270)#C
 Beep(196, 200)#G
 
 Traceback (most recent call last):
   File /Volumes/PICKLES/School/MyClass/Comp. Sci/Chapter 02 
 Stuff/program2_cep.py, line 5, in module
 from winsound import Beep
 ImportError: No module named 'winsound'
 

Looking at this, /Volumes/PICKLES/School/... that looks like a Mac filesystem 
mount point name to me.  Looks like you're using something that works on 
Windows at school, then trying to use it on a non-Windows system at home.

Try looking for a sound library which works on all platforms.  Failing that, 
look for something that works on a mac.

As a side note, you probably want to replace all those Beep() calls with some 
code which reads in a set of note values as data.
___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] optparse.OptionParser options in alphabetical order in help display

2012-12-18 Thread Steve Willoughby

Although it is probably too obvious to be the answer you're looking for, why 
can't you just add them in order in the source code?

This way, you can arrange them however you want them to appear, instead of 
python arbitrarily enforcing its own order. Python likes being explicit about 
things like that.

rail shafigulin rail.shafigu...@gmail.com wrote:

Does anybody know if there is a way to make --help option to display
options in alphabetical order? Right now it displays options in the
order I
added them. I'm using Python 3.1

Any help is appreciated.
Thanks.




___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor

-- 
Sent from my Android phone with K-9 Mail. Please excuse my brevity.___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor

[Tutor] (no subject)

2012-11-07 Thread steve clarke


Hi, I am trying to write a programme to count how many times a random point 
lies within the positive sector of a circle. So far I can display if the point 
lies inside the area but I need something to allow me to count the total number 
of items that lie inside the area. My programme is: import random for i 
in range(10):  x = random.random() y = random.random() count = 0   
if x*x + y*y  1:   count = count + 1   print count

and I get a list down the screen like1
depending on how many times a random point lies in the area. I am meant to do 
this with 1 points so I can't simply count the 1's up like I can with 10. I 
have been looking on the internet but cant find anything that works yet. 
Thanks for your timeSteve Clarke  ___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] help me decide

2012-09-05 Thread Steve Willoughby


On 05-Sep-12 10:40, Alan Gauld wrote:

On 05/09/12 11:04, Matthew Ngaha wrote:


also please could you tell me why you suggest wxPython over GTK?


Support, there are probably more beginner friendly resources for
wxPython than for GTk, although that is changing.


Yeah, and wxPython is a large, comprehensive package that should handle 
all of your GUI needs and then some.  I wrote one tool using wxPython 
and was quite happy with the results, and pleasantly surprised at the 
performance of widget updates and refreshes it achieved, even for the 
bits in pure Python.



that wxPython is the easiet to pick up yet a lot more complete than
Tkinter?


Not sure about that.  I started Tk programming back (way back) in my 
Tcl/Tk phase years ago, so I'm really used to Tk and that may bias me, 
but I'd say Tkinter is a lot easier to learn than wxPython, partly 
because it's smaller with fewer moving parts to tweak.  And yet, Tkinter 
is complete enough to be quite satisfactory for a lot of applications. 
Even after using wx, I've gone back to Tkinter when it sufficed for my 
applications, since it's a little easier to use and is a lot easier to 
distribute, coming for free with Python and all that.



this has interested me. is embedded programming a different field to
the type of programming in Python?


Yes, it is usually done using assembler and C or C++.
Some embedded work nowadays is done in Java - a reflection
of how cheap memory has become!


Right.  Although Java here doesn't necessarily mean the JVM is running 
on the embedded machine; it could be Java source code compiled down to 
something a compact runtime can execute.



--
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] understanding pydoc try

2012-08-30 Thread Steve Willoughby


On 30-Aug-12 08:22, Dave Angel wrote:

On 08/30/2012 10:43 AM, John Maclean wrote:

On 08/30/2012 03:05 PM, Dave Angel wrote:


snip


Thanks. This is a heck of a lot more clearer to me! BNF, huh? Another
set TLA that I don't need to know ;-)



I learned BNF in about 1972.  I've used about 35 languages since (not
counting hobby ones).  It can clarify a new language better than many
paragraphs of description.  But I've found that it's seldom completely
rigorous.


True, usually because people aren't as careful writing it as they are 
real code that needs to be executed by something.  Maybe it would help 
to start by describing your grammar to YACC, getting it to work, and 
then expressing that back out as BNF (or just leaving it in YACC code).



--
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] Recursion always returns None

2012-08-28 Thread Steve Willoughby


On 28-Aug-12 04:23, Dharmit Shah wrote:

Hello,

I am trying to do the following :

1) Ask user for the length of the word that he'd like to guess (for
hangman game).
2) Pick a random word from /usr/share/dict/words (which I understand
is not the best choice for hangman).
3) Call a function that would pick a random word to proceed further.

Below is the code for the part I described above :


I'm struggling to understand why you're using recursion here.
It serves no evident purpose for what you're doing, and given a large 
dictionary of words, could seriously tank the performance of the 
application, quite possibly run it out of resources and crash it altogether.


But since you're using recursion, note that when you make your recursive 
call, you're ignoring the return value from that call, so no returned 
value ever gets propagated out to the outer layers of recursion.


If the outermost layer took the recursion (length of the chosen word is 
wrong), it calls itself and then never takes the branch including the 
return statement at all.  (return word is never executed in that 
case). This causes the function to just 'fall off' the end which 
implicitly returns None.



HTH



[code]

#!/bin/env python
import random

def pick_random(l, ln):   # picks a random word from the list
l of length ln
 global mystery
 word = random.choice(l)
 if word.__len__() != ln:
 pick_random(l, ln)# recursion
 else:
 print Should return %s % word # prints the chosen random
word correctly
 return word  # always
return None, why? :(

if __name__ == __main__:
 ln = raw_input(How long word can you guess (number of alphabets) : )
 ln = int(ln)
 l = []
 with open(/usr/share/dict/words, r) as f:
 for i in f.readlines():
 i = i.split(\n)[0]
 if i.isalpha():
 l.append(i)

 word = pick_random(l, ln)
 print word

[/code]

Sample output :

$ python hangman.py
How long word can you guess (number of alphabets) : 6
Should return inarch
None
$

The problem is that the last line print word always prints None. I
know I am doing something wrong in the recursion part of the function
pick_random. Can someone please point what I am missing. Thank you!

Cheers,
Dharmit




--
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] Recursion always returns None

2012-08-28 Thread Steve Willoughby


On 28-Aug-12 09:03, Mark Lawrence wrote:

On 28/08/2012 16:51, Dharmit Shah wrote:


@ Steve : Thank you. As suggested by Dave Angel, I am going to try the
loop. And even before implementing it, I can feel that it's going to
be more efficient than recursion.



May I ask why you appear to be concerned with efficiency for a hangman
game?


Not the game per se, but if you're searching a file of thousands of 
words one at a time, randomly picking words and recursing if they're not 
what you intended, the hit--worst case--could be catastrophic.



--
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] Recursion always returns None

2012-08-28 Thread Steve Willoughby


On 28-Aug-12 09:13, Alan Gauld wrote:

On 28/08/12 16:51, Dharmit Shah wrote:


@Dave Angel : Thank you for the loop idea. It didn't strike me at all.


For some reason some beginners seem to find recursion a natural pattern.


There is a certain hey, you can do that? That's cool! factor when you 
first discover recursion.  When it naturally applies to a problem, it's 
still a powerful thing, but yes, it's often misapplied by beginners.



--
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] finally without try or except

2012-07-30 Thread Steve Willoughby


On 30-Jul-12 10:52, Mark Lawrence wrote:

On 30/07/2012 17:56, Tino Dai wrote:

  Is there anyway to execute a block of code at the end of a
program in
2.6 regardless of what happened before eg exiting normally or died
because
of an exception?



Sorry I'm not completely sure what you're asking for but will this help
http://docs.python.org/library/atexit.html ?


I don't think that will cover the use cases the OP asked about.  I 
suppose you could do something like


try:
   main()
finally:
   save_everything()

But I think it would be better to re-think your design.  Why must the 
final database commit (or whatever it is) happen at the end and not 
along the way?  Are there critical subsets of the code you could protect 
more locally and save after they're done?


Are you certain that the data you'll save will be accurate if the 
program crashed or was interrupted in the middle of something?


I think the block above will do what you're asking for, but I'm not sure 
what you're asking for is what will help you best.





--
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] Concatenating Strings

2012-05-28 Thread Steve Willoughby


On 28-May-12 19:00, Jeremy Duenas wrote:

and the both printed the same output……so why would I want to use ‘+’ to
add strings if there seems to be no reason too?


Juxtaposing strings only works with constants, which may be convenient
in some cases, but it won't work at all when concatenating other string 
values.


a=hello
b=world

a+b# will yield helloworld but
a b# is a syntax error

Using + is arguably preferable when you have a choice to make, since it 
works in all cases, including constants.


--
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] feedback on writing pipelines in python

2012-03-21 Thread Steve Willoughby


On 21-Mar-12 11:03, Abhishek Pratap wrote:

Hi Guys

I am  in the process of perl to python transition for good.  I wanted to


Why?  Perl is still a perfectly good tool.  Just not, IMHO, good for 
exactly the same things Python is good for.



1. stitch pipelines : I want python to act as a glue allowing me to run
various linux shell based programs. If needed wait for a program to
finish and then move on, logs if required


Look at the subprocess standard library module.  It offers a complete 
set of options for launching processes, piping their data aound, waiting 
for them, handling exceptions, and so forth.


___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] decimal precision in python

2012-02-07 Thread Steve Willoughby


On 07-Feb-12 03:15, Steven D'Aprano wrote:

Steve Willoughby wrote:

If you need lots of precision, you might consider using the decimal
class. It'll cost you speed vs. the native floating-point type but
won't cause you round-off errors.


I'm afraid that's not correct. Decimal is still subject to rounding errors.

  from decimal import Decimal
  x = 1/Decimal(3) # one third, as close as a Decimal can give
  x + x + x == 1
False


Sorry, I guess I took it for granted that was understood.  I was 
referring to round-off caused by binary representation of a number that 
by all appearances is a simple, rational, non-repeating decimal number 
expressed in base 10.


In other words, when you're adding up financial figures, you'll get an 
accurate sum without mysterious rounding off, but of course certain 
fractions which don't have a straightforward way to represent as a 
decimal value, like 1/3, are going to be an issue.  Good catch, though, 
it was better to point that out.



--
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] decimal precision in python

2012-02-06 Thread Steve Willoughby


On 06-Feb-12 07:25, Kapil Shukla wrote:

i tried writing a small code to calculate option price using the
binomial tree model. I compared my results with results of the same
program in excel. There seems to be a minor difference due to decimal
precision as excel is using 15 decimal precision and python (both 2.7
and 3.1) using 11. (at least that's what shown on shell)


If you need lots of precision, you might consider using the decimal 
class.  It'll cost you speed vs. the native floating-point type but 
won't cause you round-off errors.


natively, Python uses IEEE double-precision math for all float objects.

For a float value x, instead of just printing it, try this:

print('{0:.30f}'.format(x))


can some one guide me whats the equivalent of using a double datatype on
python and i can't use long() in 3.1 any more.


Equivalent to what degree?  Python's float class generally will get you 
where you need to go.  Also the int type automatically extends to 
arbitrary-precision integer values so you don't need explicit long 
type anymore.  (Unless I misunderstood your question there.)



Please also suggest a free editor for python which can at least repeat
previous command with a key stroke


I use vim, which has that feature.  I suspect any editor worth its salt 
does, or could be programmed to.



--
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] SEE THE QUESTION AT THE BOTTOM

2012-02-03 Thread Steve Willoughby


On 03-Feb-12 21:38, Debashish Saha wrote:

BUT I COULD NOT UNDERSTAND HOW THE COMMAND ELSE CAN WORK,THOUGH IT IS IN
THE OUTSIDE OF THE FOR LOOP IN WHICH IF COMMAND LIES.


The part that's confusing you is that it is not outside the for loop. 
It is PART of the for loop syntax.  The loop construct used is:


for variable in list:
list body
else:
else body

This means you run variable. through each element of list, executing 
list body once for each iteration, and a statement in that body may 
elect to break out of the loop prematurely.  If nothing breaks out of 
the loop (i.e., you exit the loop because the list was exhausted), 
then and only then execute else body.


It's a handy mechanism to handle the case where the for loop failed to 
find whatever it was searching for.  Most other languages I've used 
don't have this, and you end up doing messier manual logic steps to 
accomplish the same thing.


Tip:  Please don't type a message IN ALL CAPITAL LETTERS; it gives the 
impression you are shouting at your audience.


HTH,
HAND

--
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] Error Checking/Defensive Programming

2012-01-25 Thread Steve Willoughby


On 25-Jan-12 19:49, Devin Jeanpierre wrote:

On Wed, Jan 25, 2012 at 10:36 PM, Michael Lewismjole...@gmail.com  wrote:

 if number=0 or  0:


As long as we're helping with this, I'll just add a comment about this 
conditional statement.  First, if you string together two expressions 
with or between them, they must each be complete statements.

number=0 makes sense, but what does 0 mean?  You'd really write it as

if number = 0 or number  0:

However, that doesn't make sense because if number is something that 
can be compared with integers like 0, it will either be = 0 or  0, so 
the condition will always be true.  If number contains something that 
doesn't make sense to compare like that, then it just won't work (i.e., 
it'll likely throw an exception).  (usually :)



--
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] Weird Try..Except Error

2011-11-25 Thread Steve Willoughby


On 25-Nov-11 04:42, nikunj.badja...@emc.com wrote:

Hi All,

Thanks for the info.
I had Python27 and Python32 both installed togethar.
In Windows the PATH env variable, I had set Python27 exe and lib path.

But When I do
C:\  Python  [PressEnter]
I get 2.7

But when I run
C:\  script.py  [PressEnter]
The script is running with Python3.2 , thts weird because I have set my Path 
variable with Pytho27 exe and lib.

Which was causing the problem.


The problem is likely that when you installed Python 3.2, Windows 
associated the .py extension with the new 3.2 interpreter, PATH 
notwithstanding.


steve

--
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] Question on List Comprehensions

2011-11-22 Thread Steve Willoughby


On 21-Nov-11 23:49, Charles Becker wrote:

Alan, Steve, future readers,

After some re-reading and hacking I was able to discover the solution.  Since I 
raised the question here it is :

[['{0}'.format(x+1), x+1] for x in range(size)]


Just to fill out some other refinements for your information, if you're 
not planning to do anything special with the string formatting in each 
list, you don't really need to call format() when all it's doing is just 
making a string representation of the data value.  so

  '{0}'.format(x+1)
could just be
  str(x+1)

Resulting in:
  [[str(x+1), x+1] for x in range(size)]

Also, if you didn't like the repeated x+1 in there, you could just 
change the range call to go from 1..size directly:


  [[str(x), x] for x in range(1,size+1)]




--
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] \x00T\x00r\x00i\x00a\x00 ie I get \x00 breaking up every character ?

2011-11-20 Thread Steve Willoughby

Where did the string come from?  It looks at first glance like you have two 
bytes for each character instead of the one you expect.  Is this perhaps a 
Unicode string instead of ASCII?

Sent from my iPad

On 2011/11/20, at 10:28, dave selby dave6...@gmail.com wrote:

 Hi All,
 
 I have a long string which is an HTML file, I strip the HTML tags away
 and make a list with
 
 text = re.split('.*?', HTML)
 
 I then tried to search for a string with text.index(...) but it was
 not found, printing HTML to a terminal I get what I expect, a block of
 tags and text, I split the HTML and print text and I get loads of
 
 \x00T\x00r\x00i\x00a\x00  ie I get \x00 breaking up every character.
 
 Any idea what is happening and how to get back to a list of ascii strings ?
 
 Cheers
 
 Dave
 
 -- 
 
 Please avoid sending me Word or PowerPoint attachments.
 See http://www.gnu.org/philosophy/no-word-attachments.html
 ___
 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] \x00T\x00r\x00i\x00a\x00 ie I get \x00 breaking up every character ?

2011-11-20 Thread Steve Willoughby


On 20-Nov-11 12:04, Sarma Tangirala wrote:

Would the html parser library in python be a better idea as opposed to
using split? That way you have greater control over what is in the html.


Absolutely. And it would handle improper HTML (like unmatched brackets) 
gracefully where the split will just do the wrong thing.




On 20 Nov 2011 23:58, dave selby dave6...@gmail.com
mailto:dave6...@gmail.com wrote:

Hi All,

I have a long string which is an HTML file, I strip the HTML tags away
and make a list with

text = re.split('.*?', HTML)

I then tried to search for a string with text.index(...) but it was
not found, printing HTML to a terminal I get what I expect, a block of
tags and text, I split the HTML and print text and I get loads of

\x00T\x00r\x00i\x00a\x00  ie I get \x00 breaking up every character.

Any idea what is happening and how to get back to a list of ascii
strings ?

Cheers

Dave

--

Please avoid sending me Word or PowerPoint attachments.
See http://www.gnu.org/philosophy/no-word-attachments.html
___
Tutor maillist  - Tutor@python.org mailto: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



--
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] \x00T\x00r\x00i\x00a\x00 ie I get \x00 breaking up every character ?

2011-11-20 Thread Steve Willoughby

It's customary to copy the list with answers, so everyone can benefit 
who may run into the same issue, too.


On 20-Nov-11 11:38, dave selby wrote:

It came from some automated HTML generation app ... I just had the
idea of looking at in with ghex  every other character is \00
, thats mad. OK will try ans replace('\00', '') in the string
before splitting


Those bytes are there for a reason, it's not mad.  It's using wide 
characters, possibly due to Unicode encoding.  If there are special
characters involved (multinational applications or whatever), you'll 
destroy them by killing the null bytes and won't handle the case of that 
high-order byte being something other than zero.


Check out Python's Unicode handling, and character set encode/decode 
features for a robust way to translate the output you're getting.





Cheers

Dave

On 20 November 2011 19:15, Steve Willoughbyst...@alchemy.com  wrote:

Where did the string come from?  It looks at first glance like you have two 
bytes for each character instead of the one you expect.  Is this perhaps a 
Unicode string instead of ASCII?

Sent from my iPad

On 2011/11/20, at 10:28, dave selbydave6...@gmail.com  wrote:


Hi All,

I have a long string which is an HTML file, I strip the HTML tags away
and make a list with

text = re.split('.*?', HTML)

I then tried to search for a string with text.index(...) but it was
not found, printing HTML to a terminal I get what I expect, a block of
tags and text, I split the HTML and print text and I get loads of

\x00T\x00r\x00i\x00a\x00  ie I get \x00 breaking up every character.

Any idea what is happening and how to get back to a list of ascii strings ?

Cheers

Dave

--

Please avoid sending me Word or PowerPoint attachments.
See http://www.gnu.org/philosophy/no-word-attachments.html
___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor









--
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] Question about GUI applications.

2011-11-08 Thread Steve Willoughby


On 08-Nov-11 00:39, Alan Gauld wrote:

On 08/11/11 04:30, Nathaniel Trujillo wrote:

I just wrote the following GUI application. How do I get rid of the 7k
in the upper left hand corner and how to I put other stuff there like
say a picture of someone. Thanks for the help.


If you are using Windows I don't think you can, due to a bug in the
underlying Tk libraries. If you are using Linux/MacOS then there is a
function to replace the control icon.

I can't recall what it is, but its similar to the one used for setting
the title text on the Window, one of the wm_x calls.

But you might get a better response asking on the Tkinter mailing list...



I have an app I'm developing and running successfully on Windows (as 
well as OSX and Linux).  At least in this case it is able to replace the 
application icon in place of the default TK one.  The code I use is:


root = Tkinter.Tk()
root.iconbitmap(default=ico_image_filename)

(on Linux I use root.iconbitmap(bitmap='@'+xbm_filename))


--
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] Beginning Python From Perl

2011-11-08 Thread Steve Willoughby


On 08-Nov-11 14:14, Jihad Esmail wrote:

Hi! I am new to this list so stick with me. I've recently taken interest
in learning Python. I have already learned Perl. How should I go about
learning Python from Perl? Please help. Thanks!


I, too, was a long-standing Perl programmer before diving into Python. 
The most important thing, and I just can't stress this enough, is that 
you should seek to understand Python on its own terms first.  Learn the 
idioms and best practices of Python.  Perl and Python (and C and Ruby 
and Java and... and ...) each have their strengths, weaknesses, and 
their own way of approaching a problem.


If you just try to frame a program as you would in Perl, and translate 
the code into Python straight across, you'll get really crappy Python 
code and have a miserable time doing it.  Don't program in Perl in 
Python, in other words.


(Substitute Perl and Python with arbitrary languages of your choice.)


--
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] Question about GUI applications.

2011-11-08 Thread Steve Willoughby


On 08-Nov-11 16:38, Alan Gauld wrote:

I note it says this sets the bitmap for the iconified widget.
That to me means the icon on the desktop, or in the Taskbar.
Can you confirm that it also sets the icon at top left in
the title bar?


Yes, it changes the top left of the application window.

To test, I made a G image and installed it.  Here's a screenshot of 
the app window with and without that code.




--
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
attachment: tk-icon.pngattachment: g-icon.png___
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] login window using Tk


On 01-Nov-11 09:47, Chris Hare wrote:

Questions:
1. Is this the best way of doing this or is there a better way?
2. How do I exit the main loop when the user has authenticated?


Why stop the main loop and restart it?  Typically you'd setup the app, 
and start the main loop running for the duration.  Everything else is 
handled by the application's logic.


For example, you'd display the login toplevel window, and when it's 
satisfied, it can trigger the functionality which creates (or displays 
the pre-created but hidden) application window and dismisses the login 
toplevel.



--
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] GNU Emacs and Python


On 01-Nov-11 13:19, Alexander Etter wrote:

I like than .png image! It does appear vi biased though!


Not quite, notice the initial steep climb.  :)  Yes, it's 
tongue-in-cheek, but feels about right, once you master vi (or emacs) you're

able to be amazingly productive with complex operations involving
text files.

You think emacs is bad, though? Try TECO.


--
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] GNU Emacs and Python


On 01-Nov-11 13:24, Steve Willoughby wrote:

On 01-Nov-11 13:19, Alexander Etter wrote:

I like than .png image! It does appear vi biased though!


Not quite, notice the initial steep climb. :) Yes, it's tongue-in-cheek,


Oops, my mistake. If the y axis is productivity and x is time using the 
tool, then yes, a bit vi-biased.  And that makes the Visual Studio graph

make more sense as well :)



--
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] changing dictionary to lowercase

2011-10-27 Thread Steve Willoughby


On 27-Oct-11 11:25, ADRIAN KELLY wrote:


Hi all,
is it possible to change a dictionary list to lowercase..without having
to retype?
e.g. definitions={Deprecated: No longer in use, Depreciation:
fall in value of an asset}

i have tried definitions=definitions.lower()


lower() is not a dictionary method, it's a string method (i.e., 
dictionaries have no idea how to lowercase themselves, but strings do).


So what you need to do is iterate over the list of dictionary members 
and re-create a new dictionary with lowercased versions of the strings 
(that's easier than changing the dictionary in-place, especially if 
you're lowercasing the keys, since keys are immutable--you'd have to 
delete the old one and re-store the data under the lowercased key anyway)


There are several ways to do that, including loops and list comprehensions.

Does that nudge you in the right direction?

If you're still stuck, let us know.
--steve

--
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] string immutability

2011-10-24 Thread Steve Willoughby

On Mon, Oct 24, 2011 at 01:04:20PM -0500, Johan Martinez wrote:
 Hi,
 
 I am struggling to understand Python string immutability. I am able to
 modify Python string object after initializing/assigning it a value. So how
 does immutability work? I am not following it. Sorry for really stupid
 question. Any help?

No, you're actualy not. 

  s = First
  print s
 First

At this point, you have created a string object with the value First
and put that into the variable s (which is glossing over a detail about 
how Python variables realy work, but that's another topic).

  s = Second
  print s
 Second

Now you created a new string object with the value Second and stored THAT
into s, replacing the original object, which is now lost.

-- 
Steve Willoughby|  Using billion-dollar satellites
st...@alchemy.com   |  to hunt for Tupperware.
___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] string immutability

2011-10-24 Thread Steve Willoughby


On 24-Oct-11 12:17, Johan Martinez wrote:

Thanks for the replies everyone - Steve, Dave, Sander and Wayne. I
realized my wrong understanding/interpretation after posting the message
to the list, which usually  happens most of the time with me!


That happens to most of us all the time too :)  Unfortunately, with the 
lag between posting to the list and mail getting out to everyone, you'll 
probably get several replies that all say the same thing--we're not 
piling up on you, it's just a bunch of people being helpful without 
seeing that someone already answered yet.


Glad we could help.  Looking more into how Python variables work unlocks 
a lot of potential for all sorts of data structure operations that other 
languages require pointers to do, but are a lot easier when essentially 
all variables are references to objects but with the details handled 
behind the scenes for you.


--
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] password loop

2011-09-23 Thread Steve Willoughby


On 23-Sep-11 15:56, ADRIAN KELLY wrote:

Can anyone help me with the programme below; i hope you can see what i
am trying to do, if i enter the wrong password the loop goes on forever
and if i enter the right one nothing is printed...
i am a newbieall comments welcome


Remember that raw_input() is what actually asks you a question and 
stores your answer somewhere.  You only ever ask the question one time 
in your code, then keep re-checking the same value over and over, 
without anything to ever change its value.


In a case like this, it's helpful (especially if you're new to 
programming) to step through the instructions you've written for the 
computer, one at a time, and repeat to yourself what each step is 
accomplishing.


--
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] Confirmation if command worked

2011-08-25 Thread Steve Willoughby


On 25-Aug-11 01:37, Christian Witts wrote:

Good catch, it should be `if child.exitstatus != None and
child.exitstatus == 0:`


It's better form to say
if child.exitstatus is not None
instead of comparing for equality to None with the != operator.


--
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] inserting degrees symbol in plot title

2011-08-09 Thread Steve Willoughby


On 09-Aug-11 20:11, questions anon wrote:

I am creating a number of plots of temperature in degrees celsius and I
would like the title of the plot to have -  C°



UnicodeDecodeError: 'ascii' codec can't decode byte 0xb0 in position 19:
ordinal not in range(128)


Putting the Unicode character in your program is one thing, but what 
library functions you pass that data to is a factor, too.  Without 
knowing anything about matplotlib, my guess from the exception you 
quoted here is that the library is expecting ASCII characters below 128, 
so that function won't accept the special character.



--
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] How to get the keys of a dict inside a dict. ValueError: too many values to unpack

2011-08-08 Thread Steve Willoughby


On 08-Aug-11 02:20, Kayode Odeyemi wrote:

Either way, once you have the list of the keys you want to display,
print them out once as column headings


My concern is how do I print them out as columns, since writer.writerows
is currently lining them out as rows (\n)
Is there a function available for me to do this or do I have to
construct the column structure myself, possibly leveraging
the tab character or just basically construct a while loop and append
spaces to each keys found?


I would suggest using the string format() method to lay out the columns 
as you want them.  You could use tab, but if your data values vary much, 
you'll get inconsistent results (i.e., if one row's value goes past the 
next tab stop).  You'll want to create your own for loop to iterate over 
the (possibly sorted) list of values, printing each row the way you want it.




Thanks

On Mon, Aug 8, 2011 at 9:41 AM, Steve Willoughby st...@alchemy.com
mailto:st...@alchemy.com wrote:

Either way, once you have the list of the keys you want to display,
print them out once as column headings




--
Odeyemi 'Kayode O.
http://www.sinati.com. t: @charyorde




--
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] How to get the keys of a dict inside a dict. ValueError: too many values to unpack

2011-08-07 Thread Steve Willoughby


On 07-Aug-11 08:37, Kayode Odeyemi wrote:

Hello all,

Please I need help figuring out this permutation.

I have a dict like this:

x = {'pk': 1L, 'model': 'trans', 'fields': {'updated': 2011, 'tel':
3456}, {'pk': 2L, 'model': 'trans2', 'fields': {'updated': 2011,
'tel': 34510};


First of all, that's not a dict.  It's just a tuple of strings.
so, when you say:


#loop through and get the keys of each
for k,v in x:


You'll get one iteration, where k=the first string and v=the second.
However, you ignore k and v in all the code that follows, so I'm really 
confused what you're trying to do here.



 keys = dict(x).keys()


Now you try to create a dict out of a tuple of strings, which won't 
quite work as written but in principle would only have created a 
dictionary with the first string as the key, and the second as value, 
not nested dictionaries.


The dict() constructor really expects to see a sequence of key/value 
pairs, so it's going to take your sequence x as a list of two such 
pairs, and then raise an exception because the strings are not key/value 
pairs.  This would succeed if you said

  keys = dict((x,)).keys()
perhaps, but it's still not at all what you're trying to accomplish.


print keys


Note that you are re-assigning the value of keys each time through the 
loop but printing its last value after the loop exits.  Is that what you 
intended?



You're expecting Python to take a string that looks like Python source 
code and know that you want it to be interpreted as source code. 
Instead of using string values, use actual Python syntax directly, like:


 x = {
'pk': 1L,
'model': 'trans',
'fields': {
'updated': 2011,
'tel': 3456
}
}


--
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] How to get the keys of a dict inside a dict. ValueError: too many values to unpack

2011-08-07 Thread Steve Willoughby


On 07-Aug-11 09:17, Steve Willoughby wrote:


First of all, that's not a dict. It's just a tuple of strings.
so, when you say:


#loop through and get the keys of each
for k,v in x:


You'll get one iteration, where k=the first string and v=the second.
However, you ignore k and v in all the code that follows, so I'm really
confused what you're trying to do here.


I just noticed I glossed over a key point, for that to work you'd need x 
to be a sequence of such tuples.  As it stands there, you'll get an 
error because each element of x is a single string, so it can't pull two 
values out of each of them.


--
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] Running Python in script vs. Idle

2011-07-24 Thread Steve Willoughby


On 24-Jul-11 16:21, brandon w wrote:

Then I try to run it from a script in Gnome-terminal and it does not
run. I do not get output. I have to add print. to get any output like this:


When you type a Python expression at the interactive prompt in IDLE or 
the python command-line interpreter, it will take the extra step of 
printing the value of that expression for you.


That's not otherwise how Python works.  Normally you have to use a print 
command (or print() function in Python 3.x) to actually see the output.



--
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] Basic question on spaces

2011-07-19 Thread Steve Willoughby


On 19-Jul-11 20:39, Alexander Quest wrote:

Hello; I'm a new student of Python using Python Programming for
Absolute Beginners 3rd edition by Michael Dawson as my guide. This is a
basic question regarding spaces. I'm not sure how to make it so spaces
do not show up between variables and basic strings, particularly before
commas and after dollar signs, as in the simple tipper program I have
below.


You don't want to use print with a comma-separated list of values, then. 
 Your best bet would be the format string method, like this:


print 
Okay, based on that bill, a 15% tip would be ${0}, and
a 20% tip would be ${1}.
.format(percent15, percent20)


--
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] compare and arrange file

2011-07-11 Thread Steve Willoughby


On 11-Jul-11 16:50, Edgar Almonte wrote:

Thanks for the hints , what i want accomplish is sort the line by the
same value in the column 2 and 3

i mean the line with the same value in the 2 get together with the
line in the same value in column 3


What if the same value appears more than once?  Does it matter which 
ones you match up?  If so, how do you decide?


--
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] compare and arrange file

2011-07-11 Thread Steve Willoughby


On 11-Jul-11 17:18, Edgar Almonte wrote:

this is just one time thing and the value don't get repeat


Then you could make a single loop over the input lines, building two
dictionaries as you go:
  * one that maps column 2's value to the rest of that line's data
  * and one that does this for column 3's value.

Now run through the column 2 data you saved, print that data row,
then look up the value in the other dictionary and print that after it.



On Mon, Jul 11, 2011 at 7:55 PM, Steve Willoughbyst...@alchemy.com  wrote:

On 11-Jul-11 16:50, Edgar Almonte wrote:


Thanks for the hints , what i want accomplish is sort the line by the
same value in the column 2 and 3

i mean the line with the same value in the 2 get together with the
line in the same value in column 3


What if the same value appears more than once?  Does it matter which ones
you match up?  If so, how do you decide?

--
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




--
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] problem reading script

2011-07-01 Thread Steve Willoughby


On 01-Jul-11 10:56, Corey Richardson wrote:

Excerpts from Alan Gauld's message of Fri Jul 01 13:03:40 -0400 2011:
I use and love inconsolata[0], it's a great font for programming,
and looks great as well (both on screen and off).


I like inconsolata and Envy Code R, although just to be weird I tried 
using an old OCR font and kind of got to like that too.  A little weird 
but the glyphs are certainly distinct :)


--
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] Weird tkFont behavior

2011-06-17 Thread Steve Willoughby


On 17-Jun-11 14:18, Alan Gauld wrote:

But I confess I've never used font tags (and didn't even know
they existed).


Neither did I until now.  I had been playing with WxPython previously 
(which is still a great toolkit I'd recommend when it makes sense), but 
I've been getting happier to see the improvements to what you can do 
with just plain Tkinter since the last time I used it seriously. 
Tkinter and ttk do have the advantage of already being right there in 
the standard library.

--
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

[Tutor] Weird tkFont behavior

2011-06-16 Thread Steve Willoughby

I'm probably just doing something stupid, but I can't spot the error.  I 
hope someone here can see what I'm looking past, or knows of a known 
issue with these widgets.


I'm writing a GUI app using ttk widgets in Tkinter, which includes text 
displayed in a regular text widget.  Some text in the widget will be in 
Italics, some bold, some both, some regular.  I assigned those font 
effects as tags for the text widget as you can see in the code below.


However, when I run it, about 10% of the time, the text widget will come 
up with random fonts (e.g., bold italic instead of plain roman), even 
though I confirmed that it's using 'rm' as the tag when inserting the 
text into the widget.


The initial setup code includes:
f = Tkinter.Text(self, ...)
f.tag_config('rm', font=tkFont.Font(family='Helvetica', size=10, 
weight=tkFont.NORMAL, slant-tkFont.ROMAN))
f.tag_config('bf', font=tkFont.Font(family=Helvetica', size=10, 
weight=tkFont.BOLD, slant=tkFont.ROMAN))
f.tag_config('it', font=tkFont.Font(family=Helvetica', size=10, 
weight=tkFont.NORMAL, slant=tkFont.ITALIC))
f.tag_config('bi', font=tkFont.Font(family=Helvetica', size=10, 
weight=tkFont.BOLD, slant=tkFont.ITALIC))
f.tag_config('ref', font=tkFont.Font(family=Helvetica', size=10, 
weight=tkFont.NORMAL, slant=tkFont.ITALIC), foreground='blue', 
underline=True)


text is inserted simply by:
f.insert(END, text, 'rm')

and yet some of the time, even though the 'rm' tag is there, I get one 
of the other fonts I configured for the other tags.  Do I need to keep 
other references to the tkFont objects somewhere else or something?



--
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] Weird tkFont behavior

2011-06-16 Thread Steve Willoughby


On 16-Jun-11 09:52, Steve Willoughby wrote:

I'm probably just doing something stupid, but I can't spot the error. I
hope someone here can see what I'm looking past, or knows of a known
issue with these widgets.


I think I solved it, actually.. as I was typing this up, I wondered in 
passing about this:



of the other fonts I configured for the other tags. Do I need to keep
other references to the tkFont objects somewhere else or something?


and I think that was it.  I recoded it so that I store the Font objects 
independently of the tag configuration call, in case they were getting 
destroyed accidentally somewhere (I know you have to do that with other 
Tk objects such as images), and now I can't get the app to fail.


If interested, here's the new setup code:

|  f=Tkinter.Text(self, ...)
|
|  self.font_tags = {}
|  for tag, weight, slant, others in (
|('rm', tkFont.NORMAL, tkFont.ROMAN,  {}),
|('bf', tkFont.BOLD,   tkFont.ROMAN,  {}),
|('it', tkFont.NORMAL, tkFont.ITALIC, {}),
|('bi', tkFont.BOLD,   tkFont.ITALIC, {}),
|('ref',tkFont.NORMAL, tkFont.ITALIC, {'foreground':'blue', 
'underline':True}),

|  ):
|  self.font_tags[tag] = tkFont.Font(family='Helvetica', size=10, 
weight=weight, slant=slant)

|  f.tag_config(tag, font=self.font_tags[tag], **others)


(Added | in the left column to hopefully get the text to indent right 
with some mail readers.  That's not part of the code, of course.)


--
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 puzzle with unpacking argv

2011-06-16 Thread Steve Willoughby


On 16-Jun-11 10:10, Lisi wrote:


1 from sys import argv
2
3 script, user_name = argv

I have tried every permutation of white space I could think of that might have
looked like the original, but I always get the same error:


That will work ONLY if argv has at least 2 values in it.  Your source 
code is ok as far as it goes.  Try running your script with two command 
line arguments and see what you get.  (The first argument should be the 
name of your script, incidentally).


If your script were named foo.py, then running the command:
   foo.py

would give you the error you see because argv only has 1 thing in it and 
you're trying to retrieve two.  If you ran it as:

   foo.py bar

that should work, and script would be foo.py and user_name would be bar.

You could check len(argv) first to see how many items you have before 
you try to get two values from it.


For more sophisticated argument handling, you could look at the optparse 
or argparse modules (but that's beyond the beginner level--something to 
keep in mind for later).


--
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] trying to translate and ebcidic file

2011-06-14 Thread Steve Willoughby


On 14-Jun-11 11:40, Prinn, Craig wrote:

I am looking for a way to translate and ebcidic file to ascii. Is there
a pre-existing library for this, or do I need to do this from scratch?
If from scratch and ideas on where to start?


Bear in mind that there's no 100% straight-across translation, because 
ASCII and EBCDIC each has characters that the other lacks.  However, to 
translate the character codes they share in common, you could do 
something as simple as using the translation table functionality built 
in to the string class in Python, setting up a table to convert between 
one and the other.


of course, if you are on a Unix-like system, there's already a command 
for that, to convert a file E from EBCDIC to a file A in ASCII:


 $ dd if=E of=A conv=ascii

or the other way:
 $ dd if=A of=E conv=ebcdic

--
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] Communicating Between Programs Using Raw Inputs

2011-06-14 Thread Steve Willoughby


On 14-Jun-11 15:48, Steven D'Aprano wrote:


Normally you would do this by redirecting standard input. What operating
system are you using? In Linux, you would do something like:


# run script foo.py taking input from the output of bar.py
foo.py  bar.py


Actually, no, that will send the *source code* of bar.py as the input to 
foo.py.  I think you mean:


bar.py | foo.py

which also should work in DOS as well (although less efficiently).


However, I don't know if this will actually work for raw_input. It may
not. Try it and see.


It should.



Perhaps a better way is to have your program accept a user name and
password on the command line, and only prompt for them if not given.
Then you can say:

foo.py --user=fred --password=y8Mr3@hzi


This is one way.  Another would be to use the subprocess module in 
Python which will let one program invoke another program, and have a 
file-like object on which it can write data, which the child program 
will see as its standard input (and read in to raw_input).


--
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] Communicating Between Programs Using Raw Inputs

2011-06-14 Thread Steve Willoughby

As always, Alan has given a lot of great advice and useful information. 
 There's just one piece at the end I would question, however:



On 14-Jun-11 16:36, Alan Gauld wrote:
 python reader.py  `python writer.py`

Almost, but not quite.  The backticks mean the command is executed and 
the output substituted back on the command line.  The  bracket means to 
take what follows it as a file NAME (not a data stream).  So unless 
writer.py outputs a filename, you really want something like


python writer.py | python reader.py



--
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] Objects C++ vs Python

2011-06-09 Thread Steve Willoughby


On 08-Jun-11 22:38, Ashwini Oruganti wrote:

I'm trying to learn Python, and know C++. I have a slight confusion
regarding the meaning of object in python. Here's what I've concluded
so far:

When we say object in C++, it means an instance of a class.
e.g.


This is true in both Python and C++.


int x;// x is NOT  an object, it is a *variable*


You're confusing variables and the things they hold.  x here is a 
variable which contains an int type value.  Another variable might

hold a pointer to an object.


while in python, from what i've understood so far,
  x=5
implies that there's a memory allocation (called object) that holds the
value 3, and x is the variable (or name) that is used to refer to it.


Maybe this will be more clear:

The value 5 is an integer-class object.  Full stop.  Don't even go down 
the road of thinking of memory allocation (yet).  It's an object 
floating around in Python's runtime somewhere.


x is a name you gave to that object for now, so you can refer to it 
somehow.


The big difference is that variable names in Python are really just 
names for objects (something like pointers/references in C++ but a lot 
easier to work with), while in C++ they refer to specific memory 
locations, which must be the right size for what you store into them. 
Since Python is just naming objects, there is no such problem.


That has nothing to do with what an object means.


So does the term *Object * change its meaning when we shift the context
from C++ to python?? This is a little confusing, can someone clear it up??


Not really.  I think your confusion was about variables.

--
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] Objects C++ vs Python

2011-06-09 Thread Steve Willoughby


On 08-Jun-11 23:33, Ashwini Oruganti wrote:

On Thu, Jun 9, 2011 at 11:31 AM, Steve Willoughby st...@alchemy.com
mailto:st...@alchemy.com wrote:

The value 5 is an integer-class object.


But now what is Integer-class? Isn't integer a data type? I mean there
is no concept of classes in C, and yet in C, we can write


In Python, everything is an object, so integers are objects.  In C, 
integers are a fundamental data type.  C doesn't have objects at all.


Classes are data types, too, though, (the combination of a data 
representation and the set of behaviors that define what that data does 
in your program).




int x = 5;

Will 5, then be called an integer class object?


In an object-oriented language, yes.  In C, no, since it doesn't even 
have classes.



What exactly is a class now? I thought is a collection of variables and
(or) associated functions. Am I missing something here?


But in an object oriented language such as Python, we have classes and 
objects, and integers are just another class of data objects.  In this 
case, it's a very simple data structure with an associated set of 
methods to do things like add integers together, compare them with each 
other, etc.




--
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] create an xls file using data from a txt file

2011-05-12 Thread Steve Willoughby

Maybe we're splitting hairs over semantics then.  I thought there was 
confusion about what the CLI shell was doing with file separators as 
opposed to just handing the arguments as-is to the applications (which 
is true... the CLI doesn't really process them much, it's up to the 
application.  Where in the application, though, this is dealt with is 
not where I think we disagree.  In my original response, I clarified 
that, although as a short parenthetical note:



On 12-May-11 02:25, Peter Otten wrote:

Steve Willoughby wrote:

Actually, yes, that's exactly what Python (or actually the underlying
file handling libraries it's built with) is doing on Windows.  There is


the underlying file handling libraries would be the API calls.  But 
that's not the CLI shell's doing.  Although maybe that's what you meant 
all along.


There are enough difference between the way the Windows CLI shell and 
Unix-derived command shells function in the handling of files and option 
handling that there's often confusion there which I thought was what was 
happening here too, that the OP was saying the CLI was somehow doing the 
translation.


--
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] create an xls file using data from a txt file

2011-05-11 Thread Steve Willoughby


On 11-May-11 12:14, James Reynolds wrote:

Actually, I never knew that about the windows separators, since I've
just always used the '\' out of habit.


If you want your code to run everywhere, you should use the functions in 
os.path to manipulate and build paths.


Otherwise, using \ all the time means your code will ONLY ever work on 
Windows.  Using / all the time means your code will work fine on Mac OS 
X, Linux, or other POSIX systems, and PROBABLY ok on Windows most of the 
time, but not on other systems.



out path = 'C:\\test.xls', which will be 'C:\test.xls' or you can
write out path = r'C:\test.xls' the r bit tells python that the
following is a regular expression. or regex.


Not to be too pedantic, but since this is a tutorial list, I'll point 
out the more accurate answer so new programmers don't get a mistaken 
impression.


The 'r' string prefix does not actually mean regular expressions.  It 
means raw string where (almost) no backslash codes are recognized in 
the string constant, so you could say r'C:\test.xls' instead of 
'c:\\test.xls'.


Raw strings are, however, really useful for strings which hold regular 
expressions, so you see them in that context a lot.


... ah... and I just noticed that this was pointed out later in the 
thread.  Sorry for the repeat there.



‘/’ is perfectly valid Windows separator. See the *tested* examples
below. It works just fine pretty much anywhere I have ever tried it,
including the command line. (except apparently for an MSOffice file
save dialog that I tried just now)


Not... quite.  / is accepted by a number of programs, including the 
Python interpreter, which came from Unix-like systems where / is the 
directory separator.  Very old versions of MSDOS could be configured to 
use / on the command line for pretty much everything, but that has been 
deprecated for a long time now (they originally wanted / for 
command-line switches instead, so used \ for directory separators).


Core windows commands don't generally accept it, including native 
Windows applications (although sometimes they're lenient in what they 
accept).  It'll work for command-line Python script usage because it's 
*python* that allows them, not *windows*.


--
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] create an xls file using data from a txt file

2011-05-11 Thread Steve Willoughby

On 11-May-11 15:54, Prasad, Ramit wrote:

Core windows commands don't generally accept it, including native
Windows applications (although sometimes they're lenient in what they
accept). It'll work for command-line Python script usage because it's
*python* that allows them, not *windows*.

They work in *Windows* command prompt natively.

Respectfully, I think you aren't clear on how command line execution
works. Hopefully I can help a little (yes, there are enough cases where
it'll bite you that it's good to know this).

Some apps do not work well that is true, but the reason that theywork like this with Python is NOT because Python allows it but because
Windows does. I highly doubt Python checks for / and converts it to
\\ (or does any complicated checking of file strings). YMMV for apps,
but I have never had a problem with '/' on the command prompt. It is an
important caveat to note that this behavior is not Guaranteed.

Actually, yes, that's exactly what Python (or actually the underlying
file handling libraries it's built with) is doing on Windows. There is
a decades-long tradition of C compilers (et al) doing this conversion
for the sake of all the ported Unix C programs that people wanted to run
on Windows (or, at the time, MSDOS).

If Windows natively supported it, then you could do this:

C:\ DIR /users/fred/desktop
C:\ DEL /temp/myfile

Or try running your Python program like

C:\ /python27/python.exe scriptname.py

That doesn't work either, because Windows is NOT in any way at all
interpreting the / characters.

So why does this work:

C:\ myscript.py /temp/myfile /users/fred/desktop

or even

C:\ \python27\python.exe myscript.py /temp/myfile

That works because Windows hands ALL of the argument strings, as-is,
with NO interpretation, to the application to deal with. In this case,
the application is Python, and Python is going to the extra work to
interpret the / characters as \ characters when you try to use them in
open() calls and the like.

--
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] Reading elements in a file

2011-05-04 Thread Steve Willoughby


On 04-May-11 11:40, Greg Christian wrote:

Python version = 2.7.1
Platform = win32
I am kind of stuck on what is probably a simple thing:
If we have a file of words like this:
“first”,”word”,”in”,”that”,”another”,”part”,”of”,”this”


It depends on exactly how just like that example the file is.
For example, if it's a comma-separated value (CSV) file, with values 
enclosed optionally in quotes (as shown in your example), you can very 
easily and yet robustly read it using the csv module in the standard 
library.


Otherwise you could use regular expressions to find text inside  
quotes and ignore the commas.  Or split on ',' then strip quotes, or...


CSV is easiest if that's a match for your problem domain.

--
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] Just started Python

2011-04-27 Thread Steve Willoughby


On 27-Apr-11 14:35, Edgar Almonte wrote:

try this :



  model=raw_input(What kind of car do you drive?)
  gallons=raw_input(How many gallons have you driven?)
  number1 = float (gallons)
  miles=raw_input(How many miles have you driven?)
  number2 = float (miles)


  try:
number1 = float (gallons)
number2 = float (miles)


Indentation error aside, you'll never reach that exception because the 
previous number1 = float(gallons) would raise one if the input was 
wrong.  Either move the try..except block to enclose the first one, or 
wait until the try...except block to do the typecast.

--
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] Problem with running Python


On 22-Apr-11 07:13, Alex Butler wrote:

Hello all,

I am new to programming on Python and am teaching myself. I have figured


Hi, Alex, welcome to programming and the Python language.

If you want to get the most out of this list, it helps to ask very 
specific questions, showing what you have tried so far to figure out 
your problem, with what results.


Including examples of your actual code and actual error messages is 
enormously helpful.



out some basics of coding, however whenever I try to run the program or
check its functionality (Alt + X on my windows) it always comes back
saying that “there’s an error in your program: invalid syntax.” However,
when it returns to the IDLE page and highlights the error, it highlights
the 7 in the python 2.7.1 above any coding. And if I am able to delete
that text, it then links the syntax error to the multiple ‘’ in the
code. Is this a common issue with a simple fix? Thanks


It sounds to me like you're confusing the actual program code with other 
stuff like the  prompt Python's interpreter types to you.  Are you 
cutting and pasting more into IDLE than the Python program code itself?


You should not have things like Python 2.7.1 or  showing up in 
your source code.


--
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] (no subject)


On 22-Apr-11 15:37, Brad Desautels wrote:

Hello, I am just learning Python 3.0 and I am working on this problem. I
need to know what the output would be.Can anybody help


What is your question?  If you want to see what its output would be... 
run it and see the output.  Is there more to your question, like what 
*should* the output be? (in which case, tell us what your output *is* 
and we can help you see why it's not what you expected).

___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] (no subject)


On 22-Apr-11 15:48, Brad Desautels wrote:

Ya, I did try to run it and I am getting a syntax error before it runs.


and the message said?  Where did it point to as the syntax error?

___
Tutor maillist  -  Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor

Re: [Tutor] Python trouble


On 22-Apr-11 11:52, Alex Butler wrote:

Ok let me try to be more clear. I am trying to write code in the IDLE
Python GUI of python 2.7. When I open the new python shell, there is a
written header as well as the three s on the left side. I now those are
used as indents and I do not type them in. However, whenever I write any
type of code and either attempt to run or click alt + x to check module,
it says “there is an error in your program: invalid syntax.” Then when
it goes back to the page to highlight the syntax error the second  is
highlighted in color as it is the problem. Before I deleted the header
from this program, it would highlight the 7 after the 2. In the header.


Okay, that's pretty much what you said last time.  What is the actual 
code you're trying to run?



If it's really complaining about  being a syntax error, it sounds 
like you're confused about where you are in the tool or extra text is 
getting pasted.


If you open a new source window (file-new) (not a shell window), and 
type some python code, that window won't have a header line or  
prompts at all, just your code.


So...

start IDLE

select File-New; new untitled window pops up

type a python program, maybe this:

 print hello

hit alt-X (although personally, I'd hit F5 instead).
It should prompt you for a file to save your new program into, then run 
it back in the other window (the shell) that has the s in it.


How, exactly, does what I just described differ from what happened to you?


--
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] (no subject)


On 22-Apr-11 16:03, Brad Desautels wrote:

Hi Steve, I am getting my error on main() I think it is possibly be an
indentation error


It should be easy to check. Make sure def main(): is all the way to 
the left, and all the lines under it are the same level as each other


but usually indentation errors say that they are indentation errors.

Look carefully at your parentheses. Does every ( have a matching )?


--
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] Run a few Python commands from a temporary filesystem when the rootfs is halted


On 22-Apr-11 16:54, Frederick Grose wrote:

With Bash, when one needs to halt the current root filesystem, to pivot
to a new filesystem, one can copy some of the command files and their
dependencies to a temporary file system and execute from that code base.


I'm not sure those words mean what you think they mean, or I'm missing 
what you're trying to do here.  halting the root filesystem? pivot? code 
base?


You're not trying to talk about jail/chroot, perhaps?

--
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] Run a few Python commands from a temporary filesystem when the rootfs is halted