[EMAIL PROTECTED] wrote:
> if __name__ == '__main__':
>
> print "Globals (For Loop):"
> try:
> for i in globals():
> print "\t%s" % i
> except RuntimeError:
> print "Only some globals() printed\n"
> else:
> print "All globals() printed\n"
>
> print "Globals (Generator):"
> try:
> print "\n".join("\t%s" % i for i in globals())
> except RuntimeError:
> print "Only some globals() printed\n"
> else:
> print "All globals() printed\n"
>
>>>> Globals (For Loop):
>>>> __builtins__
>>>> Only some globals() printed
>>>>
>>>> Globals (Generator):
>>>> __builtins__
>>>> __name__
>>>> __file__
>>>> i
>>>> __doc__
>>>> All globals() printed
>>>>
>
> Why is it with a generator I get everything out but with a for loop I
> don't? I know that globals is not read-only but I would of expected
> the same behaviour from both...
Run the for loop in the interpreter, without catching exceptions. You get
__builtins__
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
RuntimeError: dictionary changed size during iteration
Then `print globals()` shows that i has been added to the global
namespace. If you run the for loop a second time, after i exists, the
loop runs fine.
Apparently, generator comprehensions have been optimized so that they
don't expose their working variables. The generator comprehension
won't add i to the global namespace, so all is well.
Mel.
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