Micah Cowan wrote: > "Jerry Hill" <[EMAIL PROTECTED]> writes: > >> On Fri, Feb 29, 2008 at 10:01 PM, Ken Pu <[EMAIL PROTECTED]> wrote: >>> Is there a way for me keep the iterating variable in list >>> comprehension local to the list comprehension? >> Kind of. You can use a generator expression instead of a list >> comprehension, and those don't leak their internal variables into the >> enclosing scope: > > Whoa, that's cool. I didn't even think to try that, just assuming it > would do the same. > > Though now that I think about it, I don't see how it possibly could, > since it just evaluates to an object that you could pass around, and > return, using it the same way elsewhere. > Well, the fact that the bound variable in the list comprehension does indeed remain outside the construct is simply the result of an over-zealous wish to emulate for loop semantics. The original reasoning, IIRC, as that since a for loop left its bound variable at the last used value, so should a list comprehension.
This was quickly recognized as a mistake, but unfortunately not quickly enough. As it was felt that some people might already have relied on that behavior, it was retained in the interests of preserving backwards compatibility. regards Steve -- Steve Holden +1 571 484 6266 +1 800 494 3119 Holden Web LLC http://www.holdenweb.com/ -- http://mail.python.org/mailman/listinfo/python-list
