Python compare words and remove duplicates in two list of lists

December 25, 2021

I have the following lists:

list_1_test = [['hi','there','how'],['we','are','one']]
list_2_test = [['hi','you','how'],['we','not','one']]

I wish to compare the words in the list and get the following output:

list_3_test = [['there','you'],['are','not']]

I know how to do this in a simple list, for example:

list_1_test = ['hi','there','how']
list_2_test = ['hi','you','how']

list_3_test=[]
for i in list_1_test:
    if i not in list_2_test:
        list_3_test.append(i)

for i in list_2_test:
    if i not in list_1_test:
        list_3_test.append(i)

and the result is

['there', 'you']

But when it comes to list of lists, my brain is fried. The order matters. Any help is much appreciated.

>Solution :

If order doesn’t matter, you can use set operations + list comprehension:

out = [list(set(l1).union(l2) - set(l1).intersection(l2)) for l1, l2 in zip(list_1_test, list_2_test)]

Output:

[['you', 'there'], ['are', 'not']]

If order matters, you can use dict.fromkeys:

out = []
for l1, l2 in zip(list_1_test, list_2_test):
    one = dict.fromkeys(l1).keys()
    two = dict.fromkeys(l2).keys()
    out.append(list(one - two) + list(two - one))

Output: