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

Posted by rob bert
rob bert
5,041 Points

Failing test with code that appears to work.

So the fourth function appears to be working, but i'm not passing the test. if i call: print(reverse_evens([1, 2, 3, 4, 5])) i get [5, 3, 1] which appears to be correct.

slices.py 
def first_4(list1):
    out = list1[:4]
    return out

def first_and_last_4(list1):
    out = list1[:4] + list1[-4:]
    return out

def odds(list1):
    out = list1[1::2]
    return out

def reverse_evens(list1):
    out = list1[::-2]
    return out

1 Answer

Steven Parker
Steven Parker
231,248 Points
Steven Parker
Steven Parker
231,248 Points

You're half right. Your method will work when the list has an odd number of items. But when the list has an even number of items, it will return reverse odds instead.

To always return reverse evens, there's two basic strategies:

  • compute the starting position based on the list size
  • extract the even index values first, then reverse them

Either one will pass the challenge when implemented correctly.