Comparing two lists in Python (almost the same)

Question

I have two lists with values in example:

List 1 = TK123,TK221,TK132 

AND

List 2 = TK123A,TK1124B,TK221L,TK132P

What I want to do is get another array with all of the values that match between List 1 and List 2 and then output the ones that Don't match.

For my purposes, "TK123" and "TK123A" are considered to match. So, from the lists above this, I would get only TK1124B.

I don't especially care about speed as I plan to run this program once and be done with it.

Answer 1

This compares every item in the list to every item in the other list. This won't work if both have letters (e.g. TK132C and TK132P wouldn't match). If that is a problem, comment below.

list_1 = ['TK123','TK221','TK132'] 
list_2 = ['TK123A','TK1124B','TK221L','TK132P']

ans = []
for itm1 in list_1:
    for itm2 in list_2:
        if itm1 in itm2:
            break
        if itm2 in itm1:
            break
    else:
        ans.append(itm1)

for itm2 in list_2:
    for itm1 in list_1:
        if itm1 in itm2:
            break
        if itm2 in itm1:
            break
    else:
        ans.append(itm2)

print ans
>>> ['TK1124B']

Answer 2

>>> list1 = 'TK123','TK221','TK132'
>>> list2 = 'TK123A','TK1124B','TK221L','TK132P'
>>> def remove_trailing_letter(s):
...     return s[:-1] if s[-1].isalpha() else s
... 
>>> diff = set(map(remove_trailing_letter, list2)).difference(list1)
>>> diff
set(['TK1124'])

And you can add the last letter back in,

>>> add_last_letter_back = {remove_trailing_letter(ele):ele for ele in list2}
>>> diff = [add_last_letter_back[ele] for ele in diff]
>>> diff
['TK1124B']

Answer 3

For:

list_1 = ['TK123', 'TK221', 'TK132']
list_2 = ['TK123A', 'TK1124B', 'TK221L', 'TK132P']

Either of the two following snippets will yield a list of common items between two lists:

list(set(list_1).intersection(list_2))
# returns []

list(set(list_1) & set(list_2))
# returns []

To get a list of exclusive items:

list(set(list_1) ^ set(list_2)) 
# returns ['TK1124B', 'TK132P', 'TK123A', 'TK221', 'TK221L', 'TK132', 'TK123']

If you want to sort the resulting list, use the sorted method:

exclusive = list(set(list_1) ^ set(list_2)) 
sorted(exclusive)
# returns ['TK1124B', 'TK123', 'TK123A', 'TK132', 'TK132P', 'TK221', 'TK221L']