Python从列表创建多对多关系

Question

I have a list, say terms = ['A', 'B', 'C', 'D']

Which is the best way to create a list-of-lists or list-of-tuples of many-to-many relationships like this;

[['A','B'],['A','C'],['A','D'],['B','C'],['B','D'],['C','D']]

Answer 1

Using itertools.combinations() :

from itertools import combinations

list(combinations(terms, r=2))

Demo:

>>> from itertools import combinations
>>> terms = ['A', 'B', 'C', 'D']
>>> list(combinations(terms, r=2))
[('A', 'B'), ('A', 'C'), ('A', 'D'), ('B', 'C'), ('B', 'D'), ('C', 'D')]

These are tuples, not lists, but that's easily remedied if that is a problem:

>>> map(list, combinations(terms, r=2))
[['A', 'B'], ['A', 'C'], ['A', 'D'], ['B', 'C'], ['B', 'D'], ['C', 'D']]