FAQ
Hello Group,

If a reference to an imported module reaches zero will Python cleanup
everything related to that module and unload the compiled code, etc, etc...?

For example:

import sys
m = [__import__(str(x)) for x in xrange(1,4)]
del sys.modules['1']
del m[0]
print m

Is module['1'] really unloaded or just it is not reachable but still loaded?

Thanks,
Elias

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  • Gabriel Genellina at Oct 23, 2009 at 1:44 am

    En Thu, 22 Oct 2009 11:59:58 -0300, lallous <lallous at lgwm.org> escribi?:

    If a reference to an imported module reaches zero will Python cleanup
    everything related to that module and unload the compiled code, etc,
    etc...?
    The module object itself (as any other object whose reference count
    reaches zero) will be destroyed. This in turn will decrement the reference
    count of its namespace (its __dict__), and when that reaches zero it will
    decrement the reference count of any object referenced (classes defined in
    the module, global variables...). If there are no other references to
    them, they will be destroyed too, as with any other object. It's always
    the same story.
    For example:

    import sys
    m = [__import__(str(x)) for x in xrange(1,4)]
    del sys.modules['1']
    del m[0]
    print m

    Is module['1'] really unloaded or just it is not reachable but still
    loaded?
    Try with sys.getrefcount(the_module); when it reaches 2 you know
    the_module is the last reference to the object [remember that getrefcount
    always returns one more than the actual reference count]
    In your example above, after the __import__ line, there are two references
    to the module '1': one in sys.modules, and one in the m list. Once you
    remove them (with del, as in your example), the module object itself is
    destroyed, yes.

    --
    Gabriel Genellina

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