"Ken Pu" <[EMAIL PROTECTED]> writes: > Hi all, > > I observed an interesting yet unpleasant variable scope behaviour with > list comprehension in the following code: > > print [x for x in range(10)] > print x > > It outputs: > > [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] > 9 > > So the list comprehension actually creates a variable x which is > somewhat unexpected.
Yeah, it's not really desired, either. The Python Reference Manual, in the "List Displays" section, has this footnote: In Python 2.3, a list comprehension "leaks" the control variables of each "for" it contains into the containing scope. However, this behavior is deprecated, and relying on it will not work once this bug is fixed in a future release. In the meantime, of course, we can't depend on it _not_ leaking, either. > Is there a way for me keep the iterating variable in list > comprehension local to the list comprehension? Not really, AFAIK. Other than to do it within a separate block, of course, but that's rather cumbersome (writing a new function would do it, but that's more trouble than it's worth). -- Micah J. Cowan Programmer, musician, typesetting enthusiast, gamer... http://micah.cowan.name/ -- http://mail.python.org/mailman/listinfo/python-list
