cokofreedom@gmail.com wrote:
Quote:
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"
>
Quote:
Quote:
>>>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.
