subset.py

def subset(elements):
    """Generate subsets."""

    if not elements:
        yield []
        return

    head = elements[0]
    for tail in subset(elements[1:]):
        yield tail
        yield [head] + tail


x = [1, 2, 3]
print(list(subset(x)))


def sub_set(head, tail=None):
    """Generate subsets."""

    if not head:
        return

    if tail is None:
        tail = set()
        yield tail

    head = set(head)
    while head:
        t = tail.union({head.pop()})
        yield t
        yield from (set(y) for y in sub_set(head, t))


print(list(sub_set(x)))