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

reverse_evens challenge Bummer

def reverse_evens(lis): print lis[::-2]

reverse_evens([1, 2, 3, 4, 5])

Gives me the desired result in Repl.it but not in Treehouse.

def first_4(lis):
    return lis[:4]

def first_and_last_4(lis):
    return lis[:4:1] + lis[-4::1]

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

def reverse_evens(lis):
    return lis[::-2]

2 Answers

james south
.a{fill-rule:evenodd;}techdegree seal-36
james south
Front End Web Development Techdegree Graduate 33,271 Points

slicing by [::-2] doesn't return evens, it returns every other element from the end, which may or may not be the even indices. you can either test for length and cut off the last element of the list if the last index is odd, then slice every other element, or slice every other element from the start (which is always even - 0), then reverse. you can chain slice operators like[:5][::-3] etc.

Ah that's helpful. SO I did " return lis[::2] " to get every other (aka even indexes startin from 0 --> 2) and then reversed the list. Thanks!!