查找两个列表x和y之间的所有配对组合，以便y中的所有元素与x中的一个元素正好配对

Question

我试图在python3中找到两个列表x和y中元素的每个唯一组合，这样对于每个组合，列表y中的所有元素都与列表x中的一个元素配对（min(x,y)max(x,y)组合）。例如，在以下情况下：

x = ['a', 'b', 'c']
y = [1, 2, 3]

combos = get_combos(x,y)
for combo in combos:
    print(combo)

…我想写get_combos(x, y)，这样它将返回一个包含27对组合的列表，打印时，这些组合如下所示：

[('a', 1) ('a', 2) ('a', 3)]
[('a', 1) ('a', 2) ('b', 3)]
[('a', 1) ('a', 2) ('c', 3)]
[('a', 1) ('b', 2) ('a', 3)]
[('a', 1) ('b', 2) ('b', 3)]
[('a', 1) ('b', 2) ('c', 3)]
[('a', 1) ('c', 2) ('a', 3)]
[('a', 1) ('c', 2) ('b', 3)]
[('a', 1) ('c', 2) ('c', 3)]
[('b', 1) ('a', 2) ('a', 3)]
[('b', 1) ('a', 2) ('b', 3)]
[('b', 1) ('a', 2) ('c', 3)]
[('b', 1) ('b', 2) ('a', 3)]
[('b', 1) ('b', 2) ('b', 3)]
[('b', 1) ('b', 2) ('c', 3)]
[('b', 1) ('c', 2) ('a', 3)]
[('b', 1) ('c', 2) ('b', 3)]
[('b', 1) ('c', 2) ('c', 3)]
[('c', 1) ('a', 2) ('a', 3)]
[('c', 1) ('a', 2) ('b', 3)]
[('c', 1) ('a', 2) ('c', 3)]
[('c', 1) ('b', 2) ('a', 3)]
[('c', 1) ('b', 2) ('b', 3)]
[('c', 1) ('b', 2) ('c', 3)]
[('c', 1) ('c', 2) ('a', 3)]
[('c', 1) ('c', 2) ('b', 3)]
[('c', 1) ('c', 2) ('c', 3)]

我已经研究了itertools.compositions、itertools.product和itertools.permutations，但它们似乎都没有给出我想要的东西。当与zip（参见this answer）一起使用时，itertools.permutations让我感觉非常接近，但在某种意义上，结果列表是独占的，任何一个列表中的元素都不能在单个组合中重复（例如[('a', 1), ('a', 2), ('c', 3)]），这不是我想要的。itertools是否适用于此，还是需要从头开始编写

Answer 1

无导入的基本递归解决方案：

x = ['a', 'b', 'c']
y = [1, 2, 3]
def groups(d, c=[]):
  if len(c) == len(x):
    yield list(zip(c, y))
  else:
    for i in d:
       yield from groups(d, c+[i])

print(list(groups(x)))

输出：

[[('a', 1), ('a', 2), ('a', 3)], [('a', 1), ('a', 2), ('b', 3)], [('a', 1), ('a', 2), ('c', 3)], [('a', 1), ('b', 2), ('a', 3)], [('a', 1), ('b', 2), ('b', 3)], [('a', 1), ('b', 2), ('c', 3)], [('a', 1), ('c', 2), ('a', 3)], [('a', 1), ('c', 2), ('b', 3)], [('a', 1), ('c', 2), ('c', 3)], [('b', 1), ('a', 2), ('a', 3)], [('b', 1), ('a', 2), ('b', 3)], [('b', 1), ('a', 2), ('c', 3)], [('b', 1), ('b', 2), ('a', 3)], [('b', 1), ('b', 2), ('b', 3)], [('b', 1), ('b', 2), ('c', 3)], [('b', 1), ('c', 2), ('a', 3)], [('b', 1), ('c', 2), ('b', 3)], [('b', 1), ('c', 2), ('c', 3)], [('c', 1), ('a', 2), ('a', 3)], [('c', 1), ('a', 2), ('b', 3)], [('c', 1), ('a', 2), ('c', 3)], [('c', 1), ('b', 2), ('a', 3)], [('c', 1), ('b', 2), ('b', 3)], [('c', 1), ('b', 2), ('c', 3)], [('c', 1), ('c', 2), ('a', 3)], [('c', 1), ('c', 2), ('b', 3)], [('c', 1), ('c', 2), ('c', 3)]]