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

Posted by Jacqueline Bennie
Jacqueline Bennie
1,020 Points

Last Step... Make a function named reverse_evens that can perform [1,2,3,4,5] into [5,3,1]

I feel like I'm so close but it's still not saying that I'm correct. What am I doing wrong on this last step?

slices.py 
def first_4(item):
    return(item[0:4:1])

def first_and_last_4(item):
    return(item[0:4] + item[-4:])

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

def reverse_evens(item):
    return(item[-1::-2])
Joshua Esquer-Davis
Joshua Esquer-Davis
9,415 Points

You're solution will not work if the length is even you want to break this down into 2 steps one to move evenly across the list and the other to reverse the list.

item[::2][::-1]

will work for this.

1 Answer

Steven Parker
Steven Parker
229,744 Points
Steven Parker
Steven Parker
229,744 Points

Without giving any spoilers, I can tell you that there's two basic strategies for solving this challenge:

  • you can compute a starting position using the length (actually the even/odd-ness) of the list
  • you can extract even indexes first, and then reverse them with a separate slice operation

Either method will work when correctly implemented.