1，大小写翻转

>>> str='hello,GhostWU'>>> str.swapcase()'HELLO,gHOSTwu'

2，从一串字符串中，提取纯数字组合

>>> str="adfask22jkljhh3jkljhgh435">>> ''.join( [s for s in str if s.isdigit() ] )'223435'>>>

等价于：

>>> str="adfask22jkljhh3jkljhgh435">>> l = []>>> for s in str:...     if s.isdigit():...             l.append( s )... >>> l['2', '2', '3', '4', '3', '5']>>> ''.join( l )'223435'>>>

 3，统计字符的出现次数，以字符为键，大小写视为相同字符

>>> s = "abcsABCDEFabcAbcdFEA">>> s = s.lower()>>> s'abcsabcdefabcabcdfea'>>> res = dict( [ ( key, s.count( key ) ) for key in set( s ) ] )>>> res{
    'a': 5, 'c': 4, 'b': 4, 'e': 2, 'd': 2, 'f': 2, 's': 1}>>>

4，字符串去重，按原来的顺序输出

>>> s'abcccabdefdx'>>> l = list( s )>>> set_list = list( set( l ) )>>> res = set_list.sort( key=l.index )>>> res>>> set_list['a', 'b', 'c', 'd', 'e', 'f', 'x']>>>

 5，字符串反转

>>> s = 'abc'>>> s[::-1]'cba'

6，去除字符串中的数字，然后排序，如果出现相同的字母，如aA，大写字母排在小写字母的前面

#!/usr/bin/python#coding:utf-8s = 'abcDBA233ABC1'l = sorted( s )upper_list = []lower_list = []for v in l:    if v.isupper():        upper_list.append( v )    elif v.islower():        lower_list.append( v )    else:        pass#print upper_list, lower_listfor x in upper_list:    x_lower = x.lower()    if x_lower in lower_list:        lower_list.insert( lower_list.index( x_lower ), x )print ''.join( lower_list )