python - 简化嵌套 for 循环

Question

我正在寻找一种更短(可能是递归)的方法来编写以下内容:

for x1 in range(10):
    for x2 in range(10 - x1):
        for x3 in range(10 - (x1 + x2)):
            for x4 in range(10 - (x1 + x2 + x3)):
                print(x1,x2,x3,x4)

Answer 1

您想要的是过滤后的产品。使用 itertools 即可，无需递归。

from itertools import product

n=10
for x1, x2, x3, x4 in filter(lambda x: sum(x) < n, product(range(n), repeat=4)):
    print(x1, x2, x3, x4)

输出:

0 0 0 0
0 0 0 1
0 0 0 2
0 0 0 3
0 0 0 4
0 0 0 5
0 0 0 6
0 0 0 7
0 0 0 8
0 0 0 9
0 0 1 0
...
9 0 0 0