python - 具有固定长度的元组的子集

Question

我希望有一个函数 subset(("A","b","C","D"),3)，它给出以下输出:

("A","b","C")
("A","b","D")
("A","C","D")
("b","C","D")

我如何在 python 3 中执行此操作？

Answer 1

itertools.combinations 函数是专门为此目的构建的:

>>> from itertools import combinations
>>> list(combinations(("A","b","C","D"), 3))
[('A', 'b', 'C'), ('A', 'b', 'D'), ('A', 'C', 'D'), ('b', 'C', 'D')]
>>>

来自docs :

itertools.combinations(iterable, r)

Return r length subsequences of elements from the input iterable.