How to get all subsets of a set? (powerset)

Question

Given a set

{0, 1, 2, 3}

How can I produce the subsets:

[set(),
 {0},
 {1},
 {2},
 {3},
 {0, 1},
 {0, 2},
 {0, 3},
 {1, 2}         


        

Answer 1

If you're looking for a quick answer, I just searched "python power set" on google and came up with this: Python Power Set Generator

Here's a copy-paste from the code in that page:

def powerset(seq):
    """
    Returns all the subsets of this set. This is a generator.
    """
    if len(seq) <= 1:
        yield seq
        yield []
    else:
        for item in powerset(seq[1:]):
            yield [seq[0]]+item
            yield item

This can be used like this:

 l = [1, 2, 3, 4]
 r = [x for x in powerset(l)]

Now r is a list of all the elements you wanted, and can be sorted and printed:

r.sort()
print r
[[], [1], [1, 2], [1, 2, 3], [1, 2, 3, 4], [1, 2, 4], [1, 3], [1, 3, 4], [1, 4], [2], [2, 3], [2, 3, 4], [2, 4], [3], [3, 4], [4]]