方式1：

#!/usr/bin/env python

#-*- encoding: utf-8 -*-

def permutations(iterable, r=None):

    # permutations('ABCD', 2) --> AB AC AD BA BC BD CA CB CD DA DB DC

    # permutations(range(3)) --> 012 021 102 120 201 210

    pool = tuple(iterable)

    n = len(pool)

    r = n if r is None else r

    if r > n:

        return

    indices = range(n)

    cycles = range(n, n-r, -1)

    yield tuple(pool[i] for i in indices[:r])

    while n:

        for i in reversed(range(r)):

            cycles[i] -= 1

            if cycles[i] == 0:

                indices[i:] = indices[i+1:] + indices[i:i+1]

                cycles[i] = n - i

            else:

                j = cycles[i]

                indices[i], indices[-j] = indices[-j], indices[i]

                print indices

                yield tuple(pool[i] for i in indices[:r])

                break

        else:

            return

for x in  permutations(xrange(1,6),3):

    print x

 

方式2：

#/usr/bin/env python

# -*-encoding:utf-8 -*-

http://blog.csdn.net/wklken/article/details/8453107

from time import time

#生成全排列

def perm(items, n=None):

    lg=len(items)

    r=n if n is not None else lg

    for i in xrange(lg):

        v = items[i:i + 1]

        if r == 1:

            yield v

        else:

            rest = items[:i] + items[i + 1:]

            for p in perm(rest, r - 1):

                yield v + p

#生成组合         

def comb(items, n=None):

    if n is None:

        n = len(items)    

    for i in xrange(len(items)):

        v = items[i:i + 1]

        if n == 1:

            yield v

        else:

            rest = items[i + 1:]

            for c in comb(rest, n - 1):

                yield v + c

                

if __name__=='__main__':

    t=time()

    for i in perm(range(1,20),3):

        print i

    print 'use time:',time()-t

 

#!/usr/bin/env python

# -*- encoding:utf-8 -*-

from time import time

def permutations(lst,n=None):

    num=len(lst)

    if num<n:

        print 'n is more than the length of list'

        return

    else:

        r= num if n is None else n       

    tmp=range(num)#用tmp值的下标对应mytup的值   

    cyc=range(num,num-r,-1)#用于循环，保证选出次数 

    yield [lst[i] for i in tmp[:r]]    

    while 1:

        for i in reversed(range(r)):

            cyc[i]-=1

            if cyc[i]==0:

                tmp[i:]=tmp[i+1:]+tmp[i:i+1]

                cyc[i] =num - i

            else:

                j=cyc[i]

                tmp[i],tmp[-j]=tmp[-j],tmp[i]

                yield [lst[i] for i in tmp[:r]]

                break

        else:

            return

if __name__=='__main__':

    t=time()        

    for x in permutations(xrange(1,20),3):

        print x

    print "total run time:",time()-t