On 07/11/2010 05:59 PM, dhruvbird wrote: > Why doesn't python's list append() method return the list itself? For > that matter, even the reverse() and sort() methods? > I found this link (http://code.google.com/edu/languages/google-python- > class/lists.html) which suggests that this is done to make sure that > the programmer understands that the list is being modified in place,
Yes! > but that rules out constructs like: > ([1,2,3,4].reverse()+[[]]).reverse() No! you can either approach this by imperatively modifying a list in-place: L = [1,2,3,4] L.reverse() L.append([]) L.reverse() Or you can use a more functional style: L2 = reversed(reversed([1,2,3,4]) + [[]]) (or ([1,2,3,4][::-1]+[[]])[::-1], if you like that kind of thing) Imagine list.reverse and list.append *did* return self: L1 = [1,2,3,4] L2 = L1.reverse().append([]).reverse() would you expect, after this code, that (L1 == L2) and (L1 is L2)? I think it would surprise a lot of people. Better clearly separate modifying an object and functionally processing an object. Cheers Thomas -- http://mail.python.org/mailman/listinfo/python-list
