Can anyone shed some light on why it is not accepting my code? When I run the function I get the right answer, which is -20.

def double_index(lst, index):

if index < len(lst):

return lst[index] * 2

else:

return lst

The solution insists on re-defining list[index] as the formula like so:

lst[index] = lst[index] * 2

but I don’t understand why this is necessary. Why can’t I just return the formula? The answer is the same.