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

Posted by Réda Berrehili
Réda Berrehili
590 Points

Hi, i get the rigth result with my function reverse_evens : [5, 3, 1] but it's not validated. what is the mistake?

Hi,

i get the rigth result with my function reverse_evens : [5, 3, 1] but it's not validated. what is the mistake?

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


def first_and_last_4(item):
    list1 = item[0:4]
    list2 = item[len(item)-4:]
    list1.extend(list2)
    return list1

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

def reverse_evens(item):
    inverse = item[-1::-1]
    return inverse[0::2]

2 Answers

Steve Hunter
Steve Hunter
57,712 Points
Steve Hunter
Steve Hunter
57,712 Points

Hi,

For the last task, you need to get the evens first, then reverse that. Otherwise, you're relying on the passed-in iterable being of an odd numbered length.

Take [1, 2, 3, 4]. The method should return the even elements, reversed, i.e. [3, 1]. If you reverse it first, like you have done, you'll take the evens out of [4, 3, 2, 1] and get [4, 2].

So, get the evens, then reverse that.

Make sense?

Steve.

Réda Berrehili
Réda Berrehili
590 Points
Réda Berrehili
Réda Berrehili
590 Points

ok thanks :)