Using list.reverse() on a subset of a list. "NoneType" object is not iterable

Question

So, I'm trying to append to one list the reverse of a subset of another list. For some reason, the interpreter doesn't seem to be liking it. Here's what I'm doing.

list1.extend(list2[someInt:someOtherInt].reverse())

Why is this not legit? It seems reasonable to me..

Answer 1

list methods operate in-place, which means that they return None.

Answer 2

In addition to Ignacio's answer, here's a solution. Try:

list1.extend(reversed(list2[someInt:someOtherInt]))

Alternatively, you can use a slice with reversed indexes, but be careful with off-by-one errors!

list1.extend(list2[someOtherInt - 1: someInt - 1: -1])

It's probably better to stick to the first method, especially as the second method will fail with 0 indexes.

Related to reversed, another trick is instead of list1.sort() you can use sorted(list1).