Check if python list elemnts respect a pattern

I have a list that looks like :

L = [2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1]

I want to check if the sequence 2-1-2 is always respected or I have an outlier somewhere .
Is there a simple way to do this with python ?

>Solution :

from itertools import cycle

L = [2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2]

seq = cycle([2, 1])

for idx, el in enumerate(L):
    if not el == next(seq):
        raise ValueError(f"Sequence not followed at index {idx}")