Write a function list_difference(numlist1, numlist2) that takes in two lists as parameters

Question

Documentation: 

Use the following template for EVERY function that you write. The docstring below should be placed inside of the function, just after the function signature.

'''

Purpose:

Parameter(s):

Return Value:

'''

Write a function list_difference(numlist1, numlist2) that takes in two lists as parameters. These lists contain numeric values and have the same length. Have the function return a new list that contains the difference between respective items in numlist1 and numlist2, without mutating either of the given lists.

Examples (text in bold is returned):

>>> alist = [5,6,7]

>>> blist = [2,2,2]

>>> list_difference(alist, blist)

[3, 4, 5]

Answer 1

Hi Panhary!

Assuming that the input lists a and b are valid inputs and have the same length, we could make a new list to store our calculated differences and append to it. But since we cannot blindly believe that the inputs are valid, we need to error check them before we perform our operations.

We need to check that the lengths of our lists are the same, and that none of them are empty. Then, we need to check that each of the elements in our lists are numbers. So we have:

def list_difference(alist, blist):

if len(alist) != len(blist):

return []

elif len(alist) == 0 or len(blist) == 0:

return []

result = []

for i in range(len(alist)):

aelem = alist[i]

belem = blist[i]

atype = type(aelem)

btype = type(belem)

if (atype != int and atype != float) or (btype != int and btype != float):

return []

result.append(aelem - belem)

return result

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