import operator
import itertools
L = [1, 1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1, 0, 0, 1, 1, 0, 0, 0, 0, 1, 1]

enumerated = list(enumerate(L))
print("enumerated", enumerated)

grouped = [(value,list(group)) for value,group in itertools.groupby(enumerated, key=operator.itemgetter(1))]
print("grouped", grouped)

filtered = [(value,group) for value,group in grouped if value != 0]
print("filtered", filtered)

result = [[index for index,_ in group] for _,group in filtered]
print("result", result)