迭代Python中的分区 [英] Iterating over partitions in Python
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问题描述
我想知道在Python中迭代分区的最佳方法是什么。
I was wondering what the best way is (in Python) to iterate over partitions of a list of a given size.
比方说,我们有列表 [1,2,3,4,5]
我们想要 k = 3
分区。这样做的一个不好的方法是写:
Say, for example, we have the list [1,2,3,4,5]
and we want k=3
partitions. A poor way of doing this would be to write:
lst = [1,2,3,4,5]
for i in range(1,len(lst)):
for j in range(i+1, len(lst)):
print lst[:i], lst[i:j], lst[j:]
这给出了
[1], [2], [3,4,5]
[1], [2,3], [4,5]
...
[1,2,3], [4], [5]
但是如果我后来想要迭代 k = 4
分区,那么我将不得不添加一个for循环嵌套级别,这在运行时无法完成。理想情况下,我想写一些类似于:
But if I later wanted to iterate over k=4
partitions, then I would have to add a level of for loop nesting, which can't be done at runtime. Ideally, I'd like to write something like:
for part in partitions([1,2,3,4,5], k):
print part
有谁知道这样做的最佳方式?
Does anyone know the best way of doing this?
推荐答案
我会使用与你相同的想法,而成对
:
I would use the same idea as yours without pairwise
:
from itertools import combinations
def partitions(items, k):
def split(indices):
i=0
for j in indices:
yield items[i:j]
i = j
yield items[i:]
for indices in combinations(range(1, len(items)), k-1):
yield list(split(indices))
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