在哪里可以找到 itertools.combinations() 函数的源代码 [英] Where can I find source code for itertools.combinations() function

问题描述

我正在尝试找到一种编写组合函数的方法.我在哪里可以找到它?

I'm trying to find a way to write a combination function. Where can I find it?

推荐答案

见itertools.combinations.这个函数有一个等效的代码:

See in the documentation of itertools.combinations. There is an equivalent code for this function:

def combinations(iterable, r):
    # combinations('ABCD', 2) --> AB AC AD BC BD CD
    # combinations(range(4), 3) --> 012 013 023 123
    pool = tuple(iterable)
    n = len(pool)
    if r > n:
        return
    indices = range(r)
    yield tuple(pool[i] for i in indices)
    while True:
        for i in reversed(range(r)):
            if indices[i] != i + n - r:
                break
        else:
            return
        indices[i] += 1
        for j in range(i+1, r):
            indices[j] = indices[j-1] + 1
        yield tuple(pool[i] for i in indices)

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