Python字符串操作

1. isalnum()判断是否都是有效字符串
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   >>> 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
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   >>> 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~

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

5. 字符的大小写转换
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   >>> ‘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
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   [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
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   [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
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   >>> 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

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   >>> 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 >>>

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   #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

    

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