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

Posted by Andrew Stokes
Andrew Stokes
9,090 Points

first and last 4 function, please help! I'm not sure where my slice when wrong?

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.

slices.py 
def first_4(arr):
    first4 = list(arr[0:4])
    return first4

def first_and_last_4(arr):
    newArr = arr[:]
    first4 = list(newArr[0:4])
    last4 = list(arr[-4:])
    newestArr = first4.extend(last4)            
    return newestArr

3 Answers

Fergus Clare
Fergus Clare
12,120 Points
Fergus Clare
Fergus Clare
12,120 Points

There is a somewhat more simple solution I believe:

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

def first_and_last_4(x):
   a = list(first_4(x)) #get a new list returned from your first function
   return a.extend(x[-4]) #extend the response from the first function with the negative index list
Daniel Svens
Daniel Svens
6,043 Points
Daniel Svens
Daniel Svens
6,043 Points

newestArr = first4.extend(last4) is the problem it doesnt actually contain the list, it contains none because extending first4 with last4 worked an no problems encountered. extend is a void function and wont return anything.

Change your code to

def first_and_last_4(arr):
    #newArr = arr[:]

    first4 = list(arr[0:4])
    last4 = list(arr[-4:])
    first4.extend(last4)
    #newestArr = first4.extend(last4)

   return first4
Hrithik Sharma
Hrithik Sharma
6,090 Points
Hrithik Sharma
Hrithik Sharma
6,090 Points

try solution
def first_and_last_4(y): first4 = y[:4] last4 = y[-4:] return first4 + last4