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

Arun Patel
Arun Patel
1,180 Points
Posted by Arun Patel
Arun Patel
1,180 Points

What's problem with reverse_evens function

def reverse_evens(str1): str2 = list(str1) list1 = str2[::-1] //First reversed the string list2 = list1[::2] //Sliced to get the even items from string return list2

slices.py 
def first_4(str1):
    str2 = list(str1)

    if len(str2) >= 4:
        list1 = str2[:4]
    else:
        return
    return list1


def first_and_last_4(str1):
    str2 = list(str1)
    if len(str2) >= 8:
        list1 = str2[:4] + str2[-4:]
    else:
        return
    return list1


def odds(str1):
    str2 = list(str1)
    list1 = str2[1::2]
    return list1

def reverse_evens(str1):
    str2 = list(str1)
    list1 = str2[::-1]
    list2 = list1[::2]
    return list2

2 Answers

Arun Patel
Arun Patel
1,180 Points
Arun Patel
Arun Patel
1,180 Points

Thanks Salmon for the clarification.

AJ Salmon
AJ Salmon
5,675 Points
AJ Salmon
AJ Salmon
5,675 Points

You have the right idea, but I think you got a little mixed up, which is easy to do with slices. The first thing you need to do is make sure you have all the even indexed items in one list, then you can reverse the list with a negative step. I changed very little in your code, so pay attention to which slice comes first; again, before you reverse the string with [::-1], you need to get all the even items into a list with [::2]. You had the right slices, just not the right order :)

def reverse_evens(str1):
    str2 = list(str1)
    list1 = str2[::2]
    list2 = list1[::-1]
    return list2