如何找到一组的所有子集,只有n个元素？

def find_subsets(arr):
    n = len(arr)
    for i in range(2**n):
        subset = []
        for j in range(n):
            if i & (1 << j):
                subset.append(arr[j])
        yield subset

arr = [1, 2, 3]
for subset in find_subsets(arr):
    print(subset)

[]
[1]
[2]
[1, 2]
[3]
[1, 3]
[2, 3]
[1, 2, 3]