I need to compare list_a against many others. my problem starts when there's a duplicated item in the other lists (two k's in other_b).

my goal is to filter out all the lists with the same items (up to three matching items).

list_a =  ['j','k','a','7']
other_b =  ['k', 'j', 'k', 'q']
other_c = ['k','k','9','k']

>>>filter(lambda x: not x in list_a,other_b)
['q']

I need a way that would return ['k', 'q'], because 'k' appears only once in list_a.

comparing list_a and other_c with set() isn't good for my purpose since it will return only one element: k. while I need ['k','9','k']

I hope I was clear enough.

Thank you