Python 获取 numpy 数组的所有排列
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Get all permutations of a numpy array
提问by MBrown
I have a numpy array [0, 1, 1, 2, 2, 0, 1, ...] which only contains the numbers 0-k. I would like to create a new array that contains the n possible arrays of permutations of 0-k. A small example with k=2 and n=6:
我有一个 numpy 数组 [0, 1, 1, 2, 2, 0, 1, ...] 它只包含数字 0-k。我想创建一个新数组，其中包含 n 个可能的 0-k 排列数组。一个 k=2 和 n=6 的小例子：
a = [0, 1, 0, 2]
permute(a)
result = [[0, 1, 0, 2]
[0, 2, 0, 1]
[1, 0, 1, 2]
[2, 1, 2, 0]
[1, 2, 1, 0]
[2, 0, 2, 1]]
Does anyone have any ideas/solutions as to how one could achieve this?
有没有人对如何实现这一目标有任何想法/解决方案？
回答by Bill Bell
Your ais what combinatorists call a multiset. The sympylibrary has various routinesfor working with them.
你的a是组合学家所说的multiset。该sympy库具有不同的程序与他们合作。
>>> from sympy.utilities.iterables import multiset_permutations
>>> import numpy as np
>>> a = np.array([0, 1, 0, 2])
>>> for p in multiset_permutations(a):
... p
...
[0, 0, 1, 2]
[0, 0, 2, 1]
[0, 1, 0, 2]
[0, 1, 2, 0]
[0, 2, 0, 1]
[0, 2, 1, 0]
[1, 0, 0, 2]
[1, 0, 2, 0]
[1, 2, 0, 0]
[2, 0, 0, 1]
[2, 0, 1, 0]
[2, 1, 0, 0]
回答by hiro protagonist
if your permutations fit in the memory, you could store them in a setand thus only get the distinguishable permutations.
如果您的排列适合内存，您可以将它们存储在 a 中set，从而只获得可区分的排列。
from itertools import permutations
a = [0, 1, 0, 2]
perms = set(permutations(a))
