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

Travis John Villanueva
Travis John Villanueva
5,052 Points

Please help. Just to get a goodnight sleep :)

I dont see why my code is wrong. I even tested it in my workspace

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

def first_and_last_4(x):
    return d

Steven Parker - Will do, thanks for the heads up.

2 Answers

So from your code, I'm assuming you're on Task 2/4.

Task 2 is: OK, this second one should be pretty similar to the first. Make a new function named first_and_last_4. It'll accept a single iterable but, this time, it'll return the first four and last four items as a single value.

So the way we can achieve this is by using a cool feature of slices. So what we can do is ask for x amount of items from the end of the list.

So for example:

# Let's say we have this list here in the variable x
x = [1, 2, 3, 4, 5, 6, 7, 8]
# We can use a negative number to get the numbers from the end of the list.
#Would return
[7, 8]

So going back to what we want to do for this question is simply get the first 4 numbers and the last four. Then return a single list with those 8 numbers.

def first_and_last_4(x):
    #To get the first four we can replicate the code created in the first task or call that function.
    first_four = x[:4]
    # Then to get the last four we simply just use a negative four to get them
    last_four = [-4:]
    # Lastly we return it.
    return first_four + last_four

An even cleaner solution would be:

def first_and_last_4(x):
    return first_4(x) + x[-4:]

This code will pass the challenge:

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

def first_and_last_4(x):
    return first_4(x) + x[-4:]

My issue with this challenge was returning the last 4 in reverse order. I was able to pass doing:

def first_and_last_4(list):
      new_result = list[:4] + list[-4:]
      return new_result