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

Austin Kosero
Austin Kosero
802 Points

What is the error with my reverse_evens function

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

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

def first_and_last_4(y):
    return y[:4]+ y[-4:]

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

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

1 Answer

Steven Parker
Steven Parker
231,269 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.