How can I compare two lists in python and return matches

Not the most efficient one, but by far the most obvious way to do it is:

>>> a = [1, 2, 3, 4, 5]
>>> b = [9, 8, 7, 6, 5]
>>> set(a) & set(b)
{5}

if order is significant you can do it with list comprehensions like this:

>>> [i for i, j in zip(a, b) if i == j]
[5]

(only works for equal-sized lists, which order-significance implies).

Use set.intersection(), it's fast and readable.

>>> set(a).intersection(b)
set([5])

I prefer the set based answers, but here's one that works anyway

[x for x in a if x in b]

Quick way:

list(set(a).intersection(set(b)))