Getting first n unique elements from Python list

Question

I have a python list where elements can repeat.

>>> a = [1,2,2,3,3,4,5,6]

I want to get the first n unique elements from

Answer 1

There are really amazing answers for this question, which are fast, compact and brilliant! The reason I am putting here this code is that I believe there are plenty of cases when you don't care about 1 microsecond time loose nor you want additional libraries in your code for one-time solving a simple task.

a = [1,2,2,3,3,4,5,6]
res = []
for x in a:
    if x not in res:  # yes, not optimal, but doesnt need additional dict
        res.append(x)
        if len(res) == 5:
            break
print(res)