[Tutor] number distribution

[Bill Jordan]

Hey everbody,

If we have 100 apples, for example, and we need to distrubte the 100 apples 
randomly in 10 boxes, how can we do this in python?

Cheers



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Re: [Tutor] number distribution

[Hugo Arts]

I suggest you take a look at the random module. There should be
something in there that suits your needs.

On Thu, Apr 22, 2010 at 2:13 PM, Bill Jordan  wrote:
> Hey everbody,
>
> If we have 100 apples, for example, and we need to distrubte the 100 apples
> randomly in 10 boxes, how can we do this in python?
>
> Cheers
>
>
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>
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Re: [Tutor] number distribution

[Alan Gauld]

"Bill Jordan"  wrote 

If we have 100 apples, for example, and we need to distrubte 
the 100 apples randomly in 10 boxes, how can we do this in python?


This sounds like homework, and we don't do homework for you.

But if you'd like to tell us your ideas, or even better show us whatever 
code you have tried to work, we can offer comments and ideas.


In the meantime try looking at the documentation for the "random" 
module.


HTH,

--
Alan Gauld
Author of the Learn to Program web site
http://www.alan-g.me.uk/

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[Tutor] sys.path and the path order

[Garry Willgoose]

My question is so simple I'm surprised I can't find an answer  
somewhere. I'm interested if I can rely on the order of the  
directories in the sys.path list. When I'm running a file from the  
comand line like


python tellusim.py

The string in entry sys.path[0] appears to be the full path to the  
location of the file I'm running in this case tellusim ... i.e. it  
looks like '/Volumes/scone2/codes/tellusim0006'. This is good because  
for my code I need to create a search path for modules that is  
relative to the location of this file irrespective of the location I'm  
in when I invoke the script file (i.e. I could be in /Volumes/scone2  
and invoke it by 'python codes/tellusim0006/tellusim.py').


The question is can I rely on entry [0] in sys.path always being the  
directory in which the original file resides (& across linux, OSX and  
Windows)? If not what is the reliable way of getting that information?







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Re: [Tutor] sys.path and the path order

[Steven D'Aprano]

On Fri, 23 Apr 2010 10:34:02 am Garry Willgoose wrote:
> My question is so simple I'm surprised I can't find an answer
> somewhere. 

Did you read the Fine Manual?


> I'm interested if I can rely on the order of the 
> directories in the sys.path list.
[...] 
> The question is can I rely on entry [0] in sys.path always being the
> directory in which the original file resides (& across linux, OSX and
> Windows)? 


The documentation says:

sys.path

A list of strings that specifies the search path for modules. 
Initialized from the environment variable PYTHONPATH, plus an 
installation-dependent default.

As initialized upon program startup, the first item of this list, 
path[0], is the directory containing the script that was used to invoke 
the Python interpreter. If the script directory is not available (e.g. 
if the interpreter is invoked interactively or if the script is read 
from standard input), path[0] is the empty string, which directs Python 
to search modules in the current directory first. Notice that the 
script directory is inserted before the entries inserted as a result of 
PYTHONPATH.

http://docs.python.org/library/sys.html#sys.path

So the answer to your question is, Yes.


-- 
Steven D'Aprano
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[Tutor] Class Inheritance

[David Hutto]

Hello List!

While experimenting with Tkinter(python2.6), when from Tkinter import*
is used I came across the following error:

C:\Users\ascent>c:\python26/Script3.py
Traceback (most recent call last):
  File "C:\python26\Script3.py", line 1, in 
from Tkinter import *
  File "C:\Python26\lib\lib-tk\Tkinter.py", line 44, in 
from turtle import *
  File "C:\Python26\lib\lib-tk\turtle.py", line 374, in 
class ScrolledCanvas(Tkinter.Frame):
AttributeError: 'module' object has no attribute 'Frame'

*

Which stems from the below in turtle.py:

class ScrolledCanvas(TK.Frame)

I know that ScrolledCanvas is trying to use class TK.Frame as it's base
class to build from, and the class Frame is what is trying to be called
from the Tkinter module.

So I tried to alter the turtle.py. When I try to just 'from Tkinter
import *, such as:

from Tkinter import *
class ScrolledCanvas(Tkinter.Frame):

I get:
*
C:\Users\ascent>c:\python26/Script3.py
Traceback (most recent call last):
  File "C:\python26\Script3.py", line 1, in 
from Tkinter import *
  File "C:\Python26\lib\lib-tk\Tkinter.py", line 44, in 
from turtle import *
  File "C:\Python26\lib\lib-tk\turtle.py", line 373, in 
class ScrolledCanvas(Tkinter.Frame):
NameError: name 'Tkinter' is not defined
***


I know pretty much what is going on there. But when I try to use:

import Tkinter
from Tkinter import *
class ScrolledCanvas(Tkinter.Frame):

It takes me back to the first error. Which means
in both instances both directly called by me, and
when called from the original turtle.py call,
it's not finding the Frame class.

>From the docs (9.5. Inheritance) it states:

"The name BaseClassName must be defined in a
scope containing the derived class definition.
In place of a base class name, other arbitrary
expressions are also allowed. This can be useful,
for example, when the base class is defined in another module:

class DerivedClassName(modname.BaseClassName)
"


So why does the above, from turtle.py, a standard module,
not allow this, or is their something
the module writer got wrong, or more likely, that I'm not
understanding about what it's doing?

As a sidenote, I ended up removing the from turtle import *
line from Tkinter which resolved the problem(the example I was using
didn't have a canvas, and I'm pretty sure Tkinter was defaulting
to the ScrolledCanvas).


TIA,
David
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Re: [Tutor] Class Inheritance

[Steven D'Aprano]

On Fri, 23 Apr 2010 03:11:36 pm David Hutto wrote:
> Hello List!
>
> While experimenting with Tkinter(python2.6), when from Tkinter
> import* is used I came across the following error:
> 
> C:\Users\ascent>c:\python26/Script3.py
> Traceback (most recent call last):
>   File "C:\python26\Script3.py", line 1, in 
> from Tkinter import *
>   File "C:\Python26\lib\lib-tk\Tkinter.py", line 44, in 
> from turtle import *
>   File "C:\Python26\lib\lib-tk\turtle.py", line 374, in 
> class ScrolledCanvas(Tkinter.Frame):
> AttributeError: 'module' object has no attribute 'Frame'

Something is screwy there. I believe you have broken your installation 
by making changes to files without having any understanding of what you 
are doing.

The turtle module does this:

import Tkinter as TK

so that line should be "class ScrolledCanvas(TK.Frame)", and in fact 
that's what I find when I go and look at the source code:

class ScrolledCanvas(TK.Frame):

The line number is different too. How many breakages have you introduced 
to the library?


> Which stems from the below in turtle.py:
>
> class ScrolledCanvas(TK.Frame)

Note the difference between Tkinter.Frame and TK.Frame.


> I know that ScrolledCanvas is trying to use class TK.Frame as it's
> base class to build from, and the class Frame is what is trying to be
> called from the Tkinter module.
>
> So I tried to alter the turtle.py. 

Please don't try to "fix" library files when you don't understand what 
they are doing. Confine your experiments to your own code, so that when 
things break, you know that the cause is in your code, not some random 
change you have done to the library.



> When I try to just 'from Tkinter 
> import *, such as:
>
> from Tkinter import *
> class ScrolledCanvas(Tkinter.Frame):

That won't work, because there is no Tkinter defined.

One wrong way to do it is:

from Tkinter import *
class ScrolledCanvas(Frame):

but that risks stomping over the top of other variables with great big 
hob-nailed boots. Better to avoid import *, and do this:

import Tkinter
class ScrolledCanvas(Tkinter.Frame):

but that's still a silly thing to do, because the turtle module has 
already imported Tkinter. The right way is to leave the module alone, 
it was working before you changed it:

import Tkinter as TK

class ScrolledCanvas(TK.Frame):


> I get:
> *
> C:\Users\ascent>c:\python26/Script3.py
> Traceback (most recent call last):
>   File "C:\python26\Script3.py", line 1, in 
> from Tkinter import *
>   File "C:\Python26\lib\lib-tk\Tkinter.py", line 44, in 
> from turtle import *
>   File "C:\Python26\lib\lib-tk\turtle.py", line 373, in 
> class ScrolledCanvas(Tkinter.Frame):
> NameError: name 'Tkinter' is not defined

Now you have two errors. 

(1) You have introduced a circular import dependency, where turtle tries 
to import Tkinter which tries to import Tkinter which tries to import 
turtle...

(2) You have no Tkinter object, since you import it's contents, not the 
module itself.


> I know pretty much what is going on there. 

I doubt it, or else you wouldn't have done what you did.

> But when I try to use: 
>
> import Tkinter
> from Tkinter import *

Why would you do that when turtle has already imported Tkinter under the 
name TK?

> class ScrolledCanvas(Tkinter.Frame):
>
> It takes me back to the first error. Which means
> in both instances both directly called by me, and
> when called from the original turtle.py call,
> it's not finding the Frame class.

I suspect you've broken it. I recommend you re-install the Tkinter 
library, including turtle.py, in order to get it back to a known 
working state.



> >From the docs (9.5. Inheritance) it states:
>
> "The name BaseClassName must be defined in a
> scope containing the derived class definition.
> In place of a base class name, other arbitrary
> expressions are also allowed. This can be useful,
> for example, when the base class is defined in another module:
>
> class DerivedClassName(modname.BaseClassName)
> "
>
>
> So why does the above, from turtle.py, a standard module,
> not allow this, or is their something
> the module writer got wrong, or more likely, that I'm not
> understanding about what it's doing?

I don't have this problem with an unmodified version of turtle and 
Tkinter in Python 2.6. I get:

>>> import turtle
>>> turtle.TK.Frame

>>> turtle.ScrolledCanvas



> As a sidenote, I ended up removing the from turtle import *
> line from Tkinter which resolved the problem(the example I was using
> didn't have a canvas, and I'm pretty sure Tkinter was defaulting
> to the ScrolledCanvas).

I should say so! Tkinter doesn't have a "from turtle import *" line, as 
that would set up a circular import dependency. No wonder you have had 
problems, making random changes to libraries without understanding 
them.




-- 
Steven D'Aprano
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