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

Paulhan Carre
Paulhan Carre
1,368 Points
Posted by Paulhan Carre
Paulhan Carre
1,368 Points

What am i doing wrong?

need help with last part

slices.py 
def first_4(a):
    return a[:4]
def first_and_last_4(fal):
    return first_4(fal) + fal[-4:]
def odds(o):
    return o[1::2]
value[2,4,6,8,10]
def reverse_evens(re):  
    return [::-1]
reverse_evens(value)
Jose Aguirre
Jose Aguirre
14,866 Points
Jose Aguirre
Jose Aguirre
14,866 Points

It seems like the first three are correct but the last one needs a little extra. Right now you are just returning the list in reverse, remember you only want elements with an even index returned so set the list equal to [::2] so that it odd index is not added to list. This is what I got.

def reverse_evens(re):
  re = re[::2]
  re = re[::-1]
  return re

Hope this helps. BTW, nice job calling the first function in the second function, that did not occur to me, but it is quite elegant.

1 Answer

Steven Parker
Steven Parker
231,236 Points
Steven Parker
Steven Parker
231,236 Points

You need to return only every other value.

This approach will only reverse the list, but you still need to return only the items that originally had even-numbered indexes.

You'll also either need to calculate the starting position based on the list size, or you'll need to extract the evens first and then reverse them in a separate step.