On Fri, Mar 21, 2014 at 8:06 PM, Rustom Mody <rustompm...@gmail.com> wrote: > Two: A comprehension variable is not bound but reassigned across the > comprehension. This problem remains in python3 and causes weird behavior when > lambdas are put in a comprehension
Because Python as a language only has the concept of assignment, not binding. I think it would be weird and confusing if variables worked this way in comprehensions and nowhere else. > >>> fl = [lambda y : x+y for x in [1,2,3]] > >>> [fl[i](2) for i in [0,1,2]] > [5, 5, 5] You can get the desired effect by adding a layer of indirection: >>> fl = [(lambda x: lambda y: x+y)(x) for x in [1,2,3]] >>> [f(2) for f in fl] [3, 4, 5] If that's too ugly then give the wrapper a proper name: >>> def make_function(x): ... return lambda y: x+y ... >>> fl = [make_function(x) for x in [1,2,3]] >>> [f(2) for f in fl] [3, 4, 5] There is also the default argument trick: >>> fl = [lambda y, *, x=x: x+y for x in [1,2,3]] >>> [f(2) for f in fl] [3, 4, 5] -- https://mail.python.org/mailman/listinfo/python-list
