Checking if a list element is inside another list if so, substitute every element inside the base list

So I currently have a bunch of mocks list such as this one. Sample:

l = ['a','a','c','d']
l2 = ['c','b','b','d']
l3 = ['c','b','b','d','x','z']
l4 = ['a','c','a','a']

What I want to do is check if any of the values inside each of these lists, is equal to any of the values inside another list.

target_l = ['a','b']

If so i want to change every element inside these lists into the matched element.

Wanted result:

l = ['a','a','a','a']
l2 = ['b','b','b','b']
l3 = ['b','b','b','b','b','b']
l4 = ['a','a','a','a']

>Solution :

Use a for loop to loop over all of the possible targets. When you see a match, replace all the elements and break:

for lst in [l, l2, l3, l4]:
    for target in target_l:
        if target in lst:
            lst[:] = [target] * len(lst)
            break

print(l, l2, l3, l4, sep='\n')

This outputs:

['a', 'a', 'a', 'a']
['b', 'b', 'b', 'b']
['b', 'b', 'b', 'b', 'b', 'b']
['a', 'a', 'a', 'a']