How can I get a reversed copy of a list (avoid a separate statement when chaining a method after .reverse)?

This code fails:

fCamel = 'F'
bCamel = 'B'
gap = ' '

k = ['F', ' ', 'B', 'F']

def solution(formation):
    return ((formation.index(bCamel) > (len(formation) - 1 - (formation.reverse()).index(fCamel))))

solution(k)

I get an exception that says AttributeError: 'NoneType' object has no attribute 'index'.

I know that the problem is that list.reverse() returns None, modifying the list in-place. I want to use .index on the reversed list. Is there a way I can avoid using a separate statement to reverse the list before indexing into it? How?

Solution

You can use reversed(formation) to return a reverse iterator of formation. When you call formation.reverse() it does an in place reversal of the list and returns None.

EDIT:

I see what you are trying to do now, in my opinion it's easier to just do this with a list comprehension:

def solution(formation):
    return len([k for k in formation[formation.index(bCamel)+1:] if k == fCamel]) == 0

This basically looks at all the elements after the first bCamel and collects all the elements that have the value fCamel. If that list has a length == 0 you have a solution.

Here's a few examples:

>>> k = ['F','F','B','B','F']
>>> solution(k)
False
>>> k = ['F','F','B','B','B']
>>> solution(k)
True
>>> k = ['F','F','B','F','F','B','B']
>>> solution(k)
False
>>>