first_and_last_4

Yes, @Wayne Ross is right. You can do it like that. But from analyzing your code, you have missed a colon in the return command of the second function. I think the logic you have tried to use is, you thought list would be first reversed and then you can take the first element to the fourth element. But since you used the command return word2[1:4:-1], what the compiler interprets whenever you specify all the three numbers in the slices it means [starting index: ending index-1: increment/decrement factor] . So it tried to find the elements in the list starting from index 1 to index 3(4-1) and the increment factor you have given is -1. Going from 1 to 3 with an increment factor of -1 is not possible, so it returns an null list. I have tried to simplify it for you with a step by step breakdown, Hope this helps.

def first_4(word):
    return word[:4]
def first_and_last_4(word):
    #list is [1,2,3,4,5,6,7,8]
    reverse_word=word[::-1]
    #Reverses the list [8,7,6,5,4,3,2,1]
    last_four_in_reverse=reverse_word[:4]
    #Gets[8,7,6,5], But answer required is [5,6,7,8] for last four, so reversing this in the next step
    last_four=last_four_in_reverse[::-1]
    answer=word[:4]+last_four
    return answer