python编写排列组合
python在编写排列组合是会用到 itertools 模块
排列
import itertools
mylist = list(itertools.permutations(['A','B','C','D'],4)) # 全排列
print(mylist)
mylist1 = list(itertools.permutations(['A','B','C','D'],3)) # 4个里面选3个排列
print(mylist1) #5!=1*2*3*4*5
#0!=1
#M个选N个 M!/(M-N)!
#4 1 4!/3!=4
#4 2 4!/2!=3*4=12
#4 3 4!/1!=24
组合
import itertools
mylist = list(itertools.combinations(['A','B','C','D'],4)) # 组合
print(mylist)
mylist1 = list(itertools.combinations(['A','B','C','D'],3)) # 4个里面选3个组合
print(mylist1) #['A','B','C','D'],3) 4个取3个,无序
#M!/N!(M-N)!
可以重复的排序(类似密码)
import itertools
# product 可以重复的排序
# mylist1 = list(itertools.product("0123456789",repeat=4)) 参数表示可以重复的从前面的0到9里面取出4个数字来
# print(mylist1)
mylist=(["".join(x) for x in itertools.product("",repeat=4) ])
print(mylist)
print(len(mylist))
利用生成器可以跌代的生产密码,节约内存
#百度云,输入密码 _ _ _ _
import itertools
# product 可以重复的排序
mylist=("".join(x) for x in itertools.product("",repeat=4))
print(next(mylist))
print(next(mylist))
print(next(mylist))
print(next(mylist))