python组合数

my_combination.py

def my_combination(arr, ns):
    '''从arr中取若干组大小分别为ns[0], ns[1], ...的数据
    '''
    if sum(ns) != len(arr):
        return
    def rec(arr, ns, result):
        if ns:
            for subset in combinations(arr, ns[0]):
                another_result = result.copy()
                another_result.append(subset)
                rest = [item for item in arr if item not in subset]
                yield from rec(rest, ns[1:], another_result)
        else:
            yield result
    yield from rec(arr, ns, [])