在 Python 中迭代分区

2022-01-24 00:00:00 python list loops iteration

问题描述

我想知道(在 Python 中)迭代给定大小列表的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.

例如，我们有列表 [1,2,3,4,5] 并且我们想要 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:]

这给了

[1], [2], [3,4,5]
[1], [2,3], [4,5]
...
[1,2,3], [4], [5]

但如果我以后想要迭代 k=4 分区，那么我将不得不添加一个级别的 for 循环嵌套，而这在运行时无法完成.理想情况下，我想写这样的东西:

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

有谁知道最好的方法?

解决方案

如果没有pairwise，我会使用和你一样的想法:

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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