#  test permutations and combinations import itertools as itfor i in it.combinations('abcd',2):    print (i)for j in it.combinations('123456',4):    print (j)for k in it.permutations('ABCDEF',2):    print (k)for m in it.product('ZXY','1234'):    print (m)lists = ['a','b','c']print (list(itertools.permutations(lists,2)))#排列，和顺序有关print ('='*60)print (list(itertools.combinations(lists,2)))#组合，和顺序无关