The
Probably the most natural way to do what you want is to turn the lists into sets and use one of the set operations (see, e.g. docs).
all function doesn't work like that - it returns True if all the values are truthy, which for integers means non-zero. So, your call to all returns True and the value True is not in list_a, so execution enters the else branch.Probably the most natural way to do what you want is to turn the lists into sets and use one of the set operations (see, e.g. docs).