Michael Brenner wrote:
> Hi,
>
> I'm implementing a plugin-based program, structured like the example
> below (where m1 in the main module, loading m2 as a plugin). I wanted
> to use a single global variable (m1.glob in the example) to store some
> config data that the plugins can access. However, the output shown
> belown seems to imply that glob is *copied* or recreated during the
> import in m2. Am I missing something? I thought m1 should be in
> sys.modules and not be recreated during the import in m2.
>
> After browsing c.l.p, it seems that this is probably somehow due to the
> circular import. However, I do not really see why this should be a
> problem here. Interestingly, the problem disappears when I put the code
> in m1 in a real main() function instead of "if __name__" etc. Though
> this seems to solve my problem, I still want to understand what's
What happens here is that there does end up being two copies of m1: the
one named __main__ and the one imported as m1. If you think about this,
there has to be two copies -- otherwise how could sometimes __name__ be
__main__ and sometimes not.
Anyway, there are several options. The simplest one here is not to
modify anything locally from __main__ block. Instead import m1, and
modify that copy. That is:
glob = [1]
if __name__ == "__main__":
import m1
m1.glob.append(2)
print "m1.main().1:", m1.glob
m2 = __import__("m2")
m2.test()
print "m1.main().2:", glob
Regards,
-tim
> happening.
>
> Thanks,
>
> michael
>
>
> m1.py:
> ------
> glob = [1]
> if __name__ == "__main__":
> glob.append(2)
> print "m1.main().1:", glob
> m2 = __import__("m2")
> m2.test()
> print "m1.main().2:", glob
> ------
>
> m2.py:
> ------
> def test():
> import m1
> print "m2.test():", m1.glob
> -----
>
> Output:
> m1.main().1: [1, 2]
> m2.test(): [1]
> m1.main().2: [1, 2]
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