Create a list of sets of atoms

Question

Say I have an array of atoms like this:

['a', 'b', 'c']

(the length may be any)

And I want to create a list of sets that can be made with them:

[  
    ['a'], ['b'], ['c'],  
    ['a', 'b'], ['a', 'c'], ['b', 'c'],  
    ['a', 'b', 'c']  
]  

Is it possible to do it easily in python?

Maybe it's very easy to do, but I'm not getting it myself.
Thank you.

Answer 1

That sounds to me like powerset:

def powerset(iterable):
    "powerset([1,2,3]) --> () (1,) (2,) (3,) (1,2) (1,3) (2,3) (1,2,3)"
    s = list(iterable)
    return chain.from_iterable(combinations(s, r) for r in range(len(s)+1))

Answer 2

Easy. Use itertools.combinations():

from itertools import combinations

atom = list('abc')

combs = [i for j in range(1, len(atom) + 1) for i in combinations(atom, j)]

which yields:

[('a',), ('b',), ('c',), ('a', 'b'), ('a', 'c'), ('b', 'c'), ('a', 'b', 'c')]