参数数字，固定排列和组合字符串的长度

f=perm('abcdefghijklmnopqrstuvwxyz01234567890', 4)

{{{#!highlight python

生成全排列

def perm(items, n=None): if n is None: n = len(items) for i in range(len(items)): v = items[i:i+1] if n == 1: yield v else: rest = items[:i] + items[i+1:] for p in perm(rest, n-1): yield v + p

生成组合

def comb(items, n=None): if n is None: n = len(items)
for i in range(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

a = perm('abc') for b in a: print b break print '-'*20 for b in a: print b }}}