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

Posted by Terry Felder
Terry Felder
1,738 Points

i ran the example and a string, through my function and it work why won't it pass?

def reverse_evens(iterable):
    return iterable[::-2]
slices.py 
def first_4(iterable):
    return iterable[:4]

def first_and_last_4(iterable):
    first4 = iterable[:4]
    last4 = iterable[-4:]
    together = first4 + last4
    return together

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

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

2 Answers

Philip Schultz
Philip Schultz
11,437 Points
Philip Schultz
Philip Schultz
11,437 Points

Hey, The reverse evens isn't working because you are assuming the length of the list is odd, what if the length of the list is even? It would start at an odd index then skip by 2, right. So, you can do this two ways. First, you can test the length to determine if its odd or even, then return a statement accordingly. Like so,

def reverse_evens(iterable):
    if len(iterable) % 2 == 0:
        return iterable[-2::-2]
    else:
        return iterable[::-2]
    return reverse_evens

Second, you can make a list of all evens going forward, then reverse. Like so, 

def reverse_evens(iterable):
    even = iterable[::2]
    reverse_evens = even[::-1]
    return reverse_evens
Terry Felder
Terry Felder
1,738 Points
Terry Felder
Terry Felder
1,738 Points

!!!! its so awesome and frustrating realinzing the answer is so simple lol thank you