On Fri, Apr 18, 2008 at 8:29 AM, Richard Thomas <[EMAIL PROTECTED]> wrote: > I like that loop variables end up still in scope, as demonstrated so > far on this list it is quite useful, but only when there is a break > somewhere. The one that confuses me, therefore, is the dummy variables > in a generator expression leaking into the scope defining that > expression. Hence: > > x = 0 > L = [f(x) for x in range(2)] > assert x == 1
There is no genexp here -- this is a list comprehension. Generator expressions do NOT leak their control variable; LCs were originally designed to leak (to mimic a for loop's semantics exactly) and thus had to remain that way throughout 2.* -- BUT that's changed in 3.0 (download and try the alpha!), where LCs don't "leak" any more. > This is not particularly intuitive as the for loop in a generator > expression can never break; generator expressions feel more "closed". They are and always have been; list comprehensions also become that way in 3.* (can't change in 2.* for obvious reasons of backwards compatibility). Alex _______________________________________________ Python-3000 mailing list Python-3000@python.org http://mail.python.org/mailman/listinfo/python-3000 Unsubscribe: http://mail.python.org/mailman/options/python-3000/archive%40mail-archive.com
