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

Code Challenge: reverse_evens

How do i return the items with an even index, in reverse
def first_4(item):
    return item[0:4]

def first_and_last_4(item):
    slice1 = item[0:4]
    slice2 = item[-4:]
    return slice1 + slice2

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

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

3 Answers

Chris Freeman
Chris Freeman
Treehouse Moderator 62,450 Points

It can not be done in a single slice since the length of the list is unknown. You need to either use an if statement on the length of the argument, or use a slice of a slice where the first slice gets the evens then the second slice reverses it.

You can use the notation item[ ][ ] to slice a slice.

Post back if you need more help. Good luck!!!

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

am still not getting the answer. How do i put thru the if statement?

Chris Freeman
Chris Freeman
Treehouse Moderator 62,450 Points

Your first slice is close but it is selecting all elements starting with the second index. You need this step to be 2, not the starting index.

Try item[-1::2]

I tried it, but it's "not returning the right values", whatever that really means

Got it now, it worked..... thanks a lot Chris Freeman