python - compare a subset of a list and return where it exists inside the list -

i have 2 lists , b, b small subset somewhere in a.

b = ['apple','banana','carrot'] = list of length 100 somewhere contains b @ indices 12,13,14. 

i search b in , return indices 12,13,14.

my current idea 2 nested loops pattern hoping there cleaner/easier solution.

here simple possibility:

b = ['a', 'b', 'c'] = ['t', 'z', 'd', 'a', 'b', 'c', 't', 's', 'a', 'b']  [i in range(len(a)) if a[i:i+len(b)] == b] 

output: [3]

returns index of first element of list b in list a. notice if b repeated more once inside a, approach return 2 indexes b repeated in a.