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

Using set with sorted+ key

sorted(set(a), key=list(a).index)[:5]
Out[136]: [1, 2, 3, 4, 5]