get all the partitions of the set python with itertools

问题

How to get all partitions of a set?

For example, I have array [1, 2, 3]. I need to get [[1], [2], [3]], [[1], [2, 3]], [[2], [1,3]], [[3], [1, 2]], [[1, 2, 3]].

Now, I wrote this code:

def neclusters(S, K):
    for splits in itertools.combinations(range(len(S)), K):
       yield np.split(S, 1 + np.array(splits))

But that code don't return [[2],[1,3]].

I could take all permutations of the original set and run this code on them. But can this be made easier?

回答1:

I wrote this one for fun:

def partition(a_list):
    yield [[x] for x in a_list]   
    for i in range(1, len(a_list) + 1):
        _l = a_list[:]
        yield [_l.pop(i-1), _l]
    yield a_list

my_list = [1, 2, 3]
print list(partition(my_list))

#or

for p in partition(my_list):
    print p

回答2:

a = [1, 2, 3]
b = list()
for l in range(len(a)+1): b.append([c for c in combinations(a, l)])

print(b)

check this

来源：https://stackoverflow.com/questions/42704932/get-all-the-partitions-of-the-set-python-with-itertools