1. 參考
9.7. itertools — Functions creating iterators for efficient looping
2. 代碼
1 # 有序排列permutations A。 2 # 不放回抽球兩次，r參數默認為len('abc') 3 >>> for i in itertools.permutations('abc',2): 4 ... print(i) 5 ... 6 ('a', 'b') 7 ('a', 'c') 8 ('b', 'a') 9 ('b', 'c') 10 ('c', 'a') 11 ('c', 'b') 12 # 無序組合combinations C。 13 # 不放回抽球兩次，r必選 14 >>> for i in itertools.combinations('abc',2): 15 ... print(i) 16 ... 17 ('a', 'b') 18 ('a', 'c') 19 ('b', 'c') 20 21 22 23 # 笛卡爾積 24 # 放回抽球，默認repeat=1 25 # product(A, B) returns the same as: ((x,y) for x in A for y in B). 26 # repeat=2相當於for i in itertools.product('abc','abc') 27 >>> for i in itertools.product('abc',repeat=2): 28 ... print(i) 29 ... 30 ('a', 'a') 31 ('a', 'b') 32 ('a', 'c') 33 ('b', 'a') 34 ('b', 'b') 35 ('b', 'c') 36 ('c', 'a') 37 ('c', 'b') 38 ('c', 'c') 39 # 放回抽球，r必選，相當於product再去掉非自定義字典序'CBA'順序的 40 >>> for i in itertools.combinations_with_replacement('CBA', 2): 41 ... print(i) 42 ... 43 ('C', 'C') 44 ('C', 'B') 45 ('C', 'A') 46 ('B', 'B') 47 ('B', 'A') 48 ('A', 'A')