[ python-Bugs-1707255 ] lost global variables in main memory intensive execution

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Bugs item #1707255, was opened at 2007-04-25 09:45
Message generated for change (Comment added) made by gbrandl
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Category: Parser/Compiler
Group: Python 2.4
>Status: Pending
Resolution: None
Priority: 5
Private: No
Submitted By: Jordi Pujol Ahulló (jpahullo)
Assigned to: Nobody/Anonymous (nobody)
Summary: lost global variables in main memory intensive execution

Initial Comment:
Hello,

I was running a very main memory intensive program in my computer. I looked for similar bugs or troubles in the site and I didn't found any similar to this. I know that the use of global variables is not recommended by software engineering, but for special cases it is very fast to develop/test some ideas.

My problem statement is the following (very simplified and also attached):

########## BEGINNING OF CODE
#test for globals

counter_1 = 0

def modifierfunction():
    global counter_1

    #some code
    counter_1 += 1
    #some other code

def test():
    for i in range(2):
        global counter_1
        counter_1 = 0

        for j in range(10):
            modifierfunction()

        print "COUNTER_1:", counter_1

def test2():
    global counter_1
    for i in range(2):
        counter_1 = 0

        for j in range(10):
            modifierfunction()

        print "COUNTER_1:", counter_1

if __name__ == "__main__":
    test()
    test2()
########## END OF CODE

Globally speaking, it is a global variable, defined at the begining of the python file (counter_1), and it is modified in some functions within it (in this example, modifierfunction). At the end, it appear some tests that make what I need. 

If you try to run this code, it will always show the expected values in the standard out. But, let me to show you my problem.

In the beginning, I have the global statement as in test2. But I found that it only take a corrent value for the first iteration. The others it has always a zero value. I didn't understand anything.

Then, some collegue suggested me to change the place of the global statement (as in test()), and then it worked correctly, as it was expected.

I repeat. The above example works fine. But when this same structure, but with my big problem, very main memory intensive, test2() didn't work correctly.

Thank you for your attention.

Regards,

Jordi

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>Comment By: Georg Brandl (gbrandl)
Date: 2007-05-11 11:17

Message:
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user_id=849994
Originator: NO

The resulting bytecode the functions are compiled to is exactly the same,
no matter where the global statement is.

So I cannot believe that moving the global statement alone causes
something that failed to work.

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Comment By: Calvin Spealman (ironfroggy)
Date: 2007-04-28 14:59

Message:
Logged In: YES 
user_id=112166
Originator: NO

If you really think there is a bug, don't post working code, post code
that actually demonstrates the problem. Something anyone else could use to
reproduce the bug.

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You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=105470&aid=1707255&group_id=5470