Global variables and modules

Binu K S binux.lists at gmail.com
Fri Dec 24 07:16:25 CET 2004


Add these lines to test1.py and see what you get:
import test2
print 'test2.glbl postinc   ', test2.glbl

This will work as you expect.

Next try chaning glbl in test2 to a list (a mutable type). 

test2.py:
glbl = [25]

def inc_glbl():
	global glbl
	glbl[0] = glbl[0] + 1

def get_glbl():
	global glbl
	return glbl[0]

test1.py:
from test2 import glbl, inc_glbl, get_glbl

print 'glbl orig      ', glbl[0]

inc_glbl()
print 'glbl postinc   ', glbl[0]

new = get_glbl()
print 'glbl from func ', new

import test2
print 'test2.glbl postinc   ', test2.glbl

[kbinu at localhost kbinu]$ python2.2 test.py 
glbl orig       25
glbl postinc    26
glbl from func  26
test2.glbl postinc    [26]


On 23 Dec 2004 21:43:40 -0800, dkeeney at travelbyroad.net
<dkeeney at travelbyroad.net> wrote:
> 
> I have a newby type question on how global variables work between
> modules.
> 
> I have a module test2.py that defines a global variable as well as two
> functions to operate on that variable.  A script test1.py imports the
> three names and prints out values of the global between operations, and
> the results aren't what I expected.
> 
> Here is the module, test2.py
> ------------------------------------
> glbl = 25
> 
> def inc_glbl():
> global glbl
> glbl += 1
> 
> def get_glbl():
> global glbl
> return glbl
> ------------------------------------
> 
> and here is the test script, test1.py
> -------------------------------------
> 
> from test2 import glbl, inc_glbl, get_glbl
> 
> print 'glbl orig      ', glbl
> 
> inc_glbl()
> print 'glbl postinc   ', glbl
> 
> new = get_glbl()
> print 'glbl from func ', new
> --------------------------------------
> I would expect the three values to be ( 25, 26, 26 ), but what I get is
> c:\projects\pitcher_model>test1.py
> glbl orig       25
> glbl postinc    25
> glbl from func  26
> 
> ---------
> It seems that the references to 'glbl' are seeing a local copy, rather
> than the original.  This is not what the literature says should be
> happening.  I am looking for a way to share data between modules.  Can
> you advise me on my error?  I am using Python 2.3.2 from ActiveState,
> on Windows XP Pro.
> 
> Thank you
> David
> 
> --
> http://mail.python.org/mailman/listinfo/python-list
>



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