Python字符串操作

1. isalnum()判断是否都是有效字符串

   >>> ev1 = 'evilxr'
   >>> ev2 = 'ev1il2xr3'
   >>> ev3 = '.,/!@#'
   >>> a = ev1.isalnum()
   >>> print a
   True
   >>> b = ev2.isalnum()
   >>> print b
   True
   >>> c = ev3.isalnum()
   >>> print c
   False

2. isalpha和isdigit可分别判断字符串里是否都是由字符或者数字组成

   >>> ev1.isalpha()
   True
   >>> ev2.isalpha()
   False
   >>> ev2.isdigit()
   False
   >>> ev3.isdigit()
   False
   >>> ev2.isalpha()
   False
   >>> ev4.isdigit()
   True
   >>> ev4.isalpha()
   False
   >>>

   可以用来检测密码的强度~

   >>> xr = raw_input('Please input your password:')
   Please input your password:evilxr1234
   >>> xr.isalpha()
   False
   >>> xr.isdigit()
   False
   >>> xr.isalnum()
   True
   >>>

3. 判断字符的大小写

   >>> xr = raw_input('Please input your password:')
   Please input your password:EVILXR
   >>> xr.islower()    #xr的内容是小写的吗？
   False
   >>> xr.isupper()      #xr的内容是大写的吗？
   True
   >>>

4. 判断是否全由空格组成

   >>> xr1 = '          '
   >>> xr1.isspace()
   True
   >>> xr2 = '  evilxr  '
   >>> xr2.isspace()
   False
   >>>

5. 字符的大小写转换

   >>> 'evilxr'.upper()    #将小写字符全转换为大写
   'EVILXR'
   >>> 'HEY,WELCOME TO MY BLOG!'.lower()    #将大写字符全转换为小写
   'hey,welcome to my blog!'
   >>> 'Hey,My name is Evilxr!'.upper()    #大小写混合的也能转
   'HEY,MY NAME IS EVILXR!'
   >>> 'Hey,My name is Evilxr!'.lower()
   'hey,my name is evilxr!'
   >>>

6. 去掉字符串左面或者右面的空格

   [root@localhost test]# cat 1.py
   ev1 = ' ev il xr '
   print ev1
   ev2 = ev1.lstrip()    #去掉左边
   print ev2
   ev3 = ev1.rstrip()    #去掉右边
   print ev3
    
   [root@localhost test]# python 1.py
    ev il xr
   ev il xr
    ev il xr

7. 判断字符串的开始和结束

   [root@localhost test]# cat 2.py
   s1 = '.com'
   s2 = '.cn'
   s3 = 'www.'
   s4 = 'www.evilxr.com'
    
   if s4.startswith(s3):
   	print 'startswith www'
   else:
   	print 'start is not www'
   if s4.endswith(s1):
   	print 'endswith is com'
   elif s2.endswith(s2):
   	print 'endswith is cn'
   else:
   	print 'endswith is not com and cn'
   [root@localhost test]# python 2.py
   startswith www
   endswith is com
   [root@localhost test]#
    

8. replace()函数的使用，值拷贝

   >>> ev = 'www.evilxr.com'
   >>> id (ev)
   3078278264L
   >>> s1 = ev.replace('e','E')
   >>> print s1
   www.Evilxr.com
   >>> id(s1)
   3078278584L
   >>> ev1 = ev.replace('ev','EV')
   >>> print ev1
   www.EVilxr.com
   >>> id(ev1)
   3078278504L

   >>> ev2 = ev.replace('evilxr','evilxr.upper()')#upper()被当成了要被替换内容的一部分
   >>> print ev2
   www.evilxr.upper().com
   >>> ev3 = ev.replace('evilxr','evilxr'.upper())#正确的应该是这个
   >>> print ev3
   www.EVILXR.com
   >>> id(ev2)
   3078232832L
   >>> id(ev3)
   3078278704L
   >>>

   #用切片看下
   >>> ev = 'evilxr'
   >>> ev1 = ev[:3]
   >>> print ev1
   evi
   >>> ev2 = ev[4:]
   >>> print ev2
   xr
   >>> ev3 = ev[:3]+'L'+ev[4:]
   >>> print ev3
   eviLxr

9. 域名匹配

   re.match(r'^(?:[a-zA-Z0-9][a-zA-Z0-9\-]*\.)*([a-zA-Z0-9][a-zA-Z0-9\-]*?\.[a-zA-Z]{2,6}(?<!\.cn)(?:\.cn)?)$', 'a.b.124.ttt.com.cn').groups()

10. python的json.dumps输出中文，指定ensure_ascii参数为False

    Signature: json.dumps(obj, skipkeys=False, ensure_ascii=True, check_circular=True, allow_nan=True, cls=None, indent=None, separators=None, encoding='utf-8', default=None, sort_keys=False, **kw)
     
    --------------------------------------------------------------------------------------------------------
    In [11]: print json.dumps({'test':"西戎的博客园"},ensure_ascii=False)
    {"test": "西戎的博客园"}
     
    In [12]: print json.dumps({'test':"西戎的博客园"})
    {"test": "\u897f\u620e\u7684\u535a\u5ba2\u56ed"}