itertools模块中,permutations,combinations和product的使用

from itertools import permutations,combinations,product#方法一和方法二,均实现了,输入一个字符串,输出各种排列,不考虑顺序
strs = 'abc'
#方法1
def zuHe(strs):n = len(strs)if not n:return strslts = []for i in range(1,n+1):for j in permutations(strs,i):flage = True #定义一个旗帜for k in permutations(j):  #检查全排列中的某一种,是否已经存在于lts中,因为不考虑顺序# for k in permutations(j,i):  #permutations,不加参数i,默认就是全排列k_strs = ''.join(k)if k_strs in lts:flage = Falsebreakif flage:j_strs = ''.join(j)lts.append(j_strs)return lts#方法2
def zuHe2(strs):n = len(strs)if not n:return strslts = []for i in range(1,n+1):for j in combinations(strs,i):flage = True #定义一个旗帜# 检查全排列中的某一种,是否已经存在于lts中,因为不考虑顺序    combinations需要指定参数ifor k in combinations(j,i):k_strs = ''.join(k)if k_strs in lts:flage = Falsebreakif flage:j_strs = ''.join(j)lts.append(j_strs)return lts#笛卡尔,多用在组合矩阵方面
for m in product([1,2],repeat=3):print(m)'''
(1, 1, 1)
(1, 1, 2)
(1, 2, 1)
(1, 2, 2)
(2, 1, 1)
(2, 1, 2)
(2, 2, 1)
(2, 2, 2)
'''
if __name__ == '__main__':print(zuHe(strs))  #['a', 'b', 'c', 'ab', 'ac', 'bc', 'abc']print(zuHe2(strs))  #['a', 'b', 'c', 'ab', 'ac', 'bc', 'abc']