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

Posted by behar
behar
10,799 Points

What is wrong with the final step. It works perfectly fine in the shell

What wrong with this this code?

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


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


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


def reverse_evens(itr):
    del itr[1::2]
    return itr[::-1]

2 Answers

Steven Parker
Steven Parker
231,269 Points
Steven Parker
Steven Parker
231,269 Points

I tried this for myself to see that it does appear to work. But I'm baffled as to why — since a slice returns a copy of a list, I don't understand how a "del" operation performed on it can possibly affect the original list.

But as a suggestion for passing the challenge: instead of deleting the items you don't want, try extracting the ones you do want and then reversing them.

behar
behar
10,799 Points

I dont know how to do this, i tried using the pop feature but you cant say:

new_list = itr.pop([0::2])
behar
behar
10,799 Points
behar
behar
10,799 Points

Lol realised imidiately after posting that i can just do:

whatever = itr[0::2]

So i got it, ty!