python list problem

Question

i have been stuck on this question for days. any suggestions would be greatly appreciated.

slices.py

def first_4(x):
    return x[0:4]
def odds(a):
    return a[1::2]
def first_and_last_4(s):
    return s[4:0:1] 
    return s[4:0:-1]

Answer 1 · 2016-12-18T06:39:23Z

December 18, 2016 6:39am

Hi Ammar,

Although you can have multiple return statements in a function, they need to be routed through different conditions such that you will only ever return one thing at a time. If you set up 2 consecutive return statements like you have, only the first one will actually trigger.

But to solve the 3rd part of the challenge, you can actually reuse the code you wrote in task 1. This will produce the first 4 items in the list. (You can either rewrite the code in first_4() or you can just call the function instead of writing the same code twice. It doesn't really matter in this case since the code is so minimal, but it's always good practice to not repeat code you've already written if you can help it.).

To get the last 4, you need to start at the opposite end of the list using a negative index reference, so -4 would be the starting point. Then you will just increment normally to the end.

And finally, to add lists together you can simply use the plus sign.

def first_4(x):
    return x[0:4]

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

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

# Alternatively
def first_and_last_4(s):
    return first_4(s) + s[-4:]

Hope this helps.

Answer 2 · 2016-12-18T06:33:42Z

December 18, 2016 6:33am

It should actually return it as a single list .

def first_4(arg1):
    return arg1[0:4]
def odds(arg1):
    return arg1[1::2]
def first_and_last_4(arg1):
    first_4=arg1[0:4]
    last_4_inverted=arg1[-1:-5:-1]
    last_4=last_4_inverted[::-1]
    return first_4+last_4

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Ammar Fatihallah

Ammar Fatihallah

python list problem

2 Answers

Ryan S

Ryan S

Vidhya Sagar

Vidhya Sagar