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Python Python Collections (2016, retired 2019) Slices Slice Functions

John DiGiovanni
PLUS
John DiGiovanni
Courses Plus Student 902 Points
Posted by John DiGiovanni
John DiGiovanni
Courses Plus Student 902 Points

I’m getting an error that my reverse_evens function isn’t returning the correct values.

I’m getting an error message during the last step of this Slice exercise that my reverse_evens function isn’t returning the correct values. I copy pasted it into Pythonista to try and it works perfectly fine (only returning the even indexes in reverse order), what is wrong with my code?

slices.py 
def first_4(item):
    return item[:4]

def first_and_last_4(item):
    return first_4(item) + item[-4:]

def odds(item):
    return item[1::2]

def reverse_evens(item):
    return item[-1::-2]

1 Answer

AJ Salmon
AJ Salmon
5,675 Points
AJ Salmon
AJ Salmon
5,675 Points

Hey John! The problem here is that this only works if your iterable has an odd number of items in it (in other words, if the last item has an even index). So reverse_evens([1, 2, 3, 4, 5, 6]) returns [6, 4, 2], which are at indexes 5, 3, and 1, respectively. You need to find a way to make sure that you have all of the even indexes in an iterable, then you can reverse it. It should take two steps! (That's not me saying that it will necessarily be two lines of code, it's a hint ;))