On Aug 28, 9:43 pm, hwg <[EMAIL PROTECTED]> wrote: > I've searched the group and didn't see the answer to this... > > Why doesn't this work?: > > >>> letters = ['d', 'a', 'e', 'c', 'b'] > >>> letters[1:3].sort() > > This returns None. > > Why? letters[1:3] is ['a', 'e', 'c'] Sorting that should return > ['a', 'c', 'e'] > > hwg
There are a couple of flaws in your example. letters[1:3] is not ['a', 'e', 'c'], but is just ['a','e']. The elements of a slice start with the lower-bound INclusive (zero-based, so this is 'a'), up to the upper bound EXclusive (up to, but NOT INCLUDING 'c'). The slice returns a copy of the selected elements. .sort() does an in-place sort, and returns None. You may instead use the builtin function sorted(), as in: sorted(letters[1:4]) which in fact DOES return ['a', 'c', 'e']. What your example had done was: 1. choose 2 elements of a list and copy them to a temporary list 2. sort the list in place 3. return None 4. discard the temporary list, since all references to it were gone For remedial study: - study notation for slices - study the difference between list.sort() and sorted() -- Paul -- http://mail.python.org/mailman/listinfo/python-list
