Question

在Python中，我尝试在N列表列表中添加元素的所有不同组合，其中N是变量。具体来说，我正在使用包含列表[1, 2, 3, 4, 5, 6]的N个副本的列表。

所以让我们假设N = 3。我想循环浏览第一个列表，添加：

 6 + 6 + 6
 5 + 6 + 6
 ...
 1 + 6 + 6`

然后增加第二个人并开始添加：

6 + 5 + 6
5 + 5 + 6
...
1 + 1 + 1  # ultimately to

当然我增加了第三个人。这个具体的例子可以用3个嵌套的for循环来完成，但当然，我需要改变循环的数量。我在网络和这个论坛上搜索答案，并且不能完全掌握我应该做的事情。人们一直在说使用递归函数，但在我查看之前我从未听说过。所以很难掌握。

Answer 1

为了实现这一目标，您可以使用itertools.product作为：

from itertools import product
my_list = [1, 2, 3, 4, 5, 6]
N=3 

#                         value of `N` v
for s in product(my_list[::-1], repeat=N):
    print '{} : {}'.format(s[::-1], sum(s))
    #           No need to reverse here ^
    #           since sum(s[::-1]) and sum(s) will give same result

将打印：

# (combination) : sum
(6, 6, 6) : 18
(5, 6, 6) : 17
(4, 6, 6) : 16
(3, 6, 6) : 15
(2, 6, 6) : 14
(1, 6, 6) : 13
...
(6, 1, 1) : 8
(5, 1, 1) : 7
(4, 1, 1) : 6
(3, 1, 1) : 5
(2, 1, 1) : 4
(1, 1, 1) : 3

如果您只想将值存储在list中，则可以使用 list comprehension 表达式：

>>> [sum(s) for s in product(my_list[::-1], repeat=3)]
[18, 17, 16, 15, 14, 13, 17, 16, 15, 14, 13, 12, 16, 15, 14, 13, 12, 11, 15, 14, 13, 12, 11, 10, 14, 13, 12, 11, 10, 9, 13, 12, 11, 10, 9, 8, 17, 16, 15, 14, 13, 12, 16, 15, 14, 13, 12, 11, 15, 14, 13, 12, 11, 10, 14, 13, 12, 11, 10, 9, 13, 12, 11, 10, 9, 8, 12, 11, 10, 9, 8, 7, 16, 15, 14, 13, 12, 11, 15, 14, 13, 12, 11, 10, 14, 13, 12, 11, 10, 9, 13, 12, 11, 10, 9, 8, 12, 11, 10, 9, 8, 7, 11, 10, 9, 8, 7, 6, 15, 14, 13, 12, 11, 10, 14, 13, 12, 11, 10, 9, 13, 12, 11, 10, 9, 8, 12, 11, 10, 9, 8, 7, 11, 10, 9, 8, 7, 6, 10, 9, 8, 7, 6, 5, 14, 13, 12, 11, 10, 9, 13, 12, 11, 10, 9, 8, 12, 11, 10, 9, 8, 7, 11, 10, 9, 8, 7, 6, 10, 9, 8, 7, 6, 5, 9, 8, 7, 6, 5, 4, 13, 12, 11, 10, 9, 8, 12, 11, 10, 9, 8, 7, 11, 10, 9, 8, 7, 6, 10, 9, 8, 7, 6, 5, 9, 8, 7, 6, 5, 4, 8, 7, 6, 5, 4, 3]

Answer 2

您可以使用 itertools.combinations_with_replacement 来解决此问题。

In []: from itertools import combinations_with_replacement
In []: for combination in combinations_with_replacement(range(1, 7), 3):
           print("Combination: ", combination, " Sum: ", sum(combination))
   ....:     
Combination: (1, 1, 1)  Sum: 3
Combination: (1, 1, 2)  Sum: 4
Combination: (1, 1, 3)  Sum: 5
Combination: (1, 1, 4)  Sum: 6
Combination: (1, 1, 5)  Sum: 7
Combination: (1, 1, 6)  Sum: 8
.
.
.
Combination: (4, 5, 6)  Sum: 15
Combination: (4, 6, 6)  Sum: 16
Combination: (5, 5, 5)  Sum: 15
Combination: (5, 5, 6)  Sum: 16
Combination: (5, 6, 6)  Sum: 17
Combination: (6, 6, 6)  Sum: 18

如果您想将总和存储在list中，可以使用列表理解：

list_of_sums = [sum(combination) for combination in combinations_with_replacement(range(1, 7), 3)]

求和列表中所有可能的元素组合

2 个答案: