python 学习记录（1）—对内建str的处理

1.1 对str进行数据提取

 In [1]: 


 In [2]: import subprocess


 In [3]: res = subprocess.Popen(['uname','-sv'],stdout = subprocess.PIPE)


 In [4]: 
uname = res.stdout.read().strip()


 In [5]: uname

 Out[5]: 'Linux #63-Ubuntu SMP Mon Nov 28 19:23:11 UTC 2011'


 In [6]:
 '63'in uname        
 用in或not in检查一个字符串是不是另一个字符串的子串

 Out[6]: True


 In [7]: '64'in uname

 Out[7]: False


 In [8]: 
'64'not in uname

 Out[8]: True


 In [9]:
 uname.index('linux')    
 使用index或find找出字符串的具体位置

 ---------------------------------------------------------------------------

 ValueError                                Traceback (most recent call last)


 /home/lijy/<ipython console> in <module>()


 ValueError: substring not found


 In [10]: uname.index('Linux')

 Out[10]: 0


 In [11]: uname.index('Mon')

 Out[11]: 21


 In [12]: 
uname.find('Mon')

 Out[12]: 21


 In [13]: uname.find('mon')

Out[13]: -1
1.2 字符串切分
In [15]: smp_index = uname.index('SMP')       设置切分点位置

 In [16]: smp_index
 Out[16]: 17

 In [17]: uname[smp_index:]
 Out[17]: 'SMP Mon Nov 28 19:23:11 UTC 2011'             输出冒号右边内容

 In [18]: uname[:smp_index]                                   输出冒号左边内容
 Out[18]: 'Linux #63-Ubuntu '

 In [19]: uname
 Out[19]: 'Linux #63-Ubuntu SMP Mon Nov 28 19:23:11 UTC 2011'

 In [20]: 1.3 判断是否以某一字符串开始或结束
In [23]: test_string = 'i am a student'

 In [24]: test_string.startwith('i')
 ---------------------------------------------------------------------------
 AttributeError                            Traceback (most recent call last)

 /home/lijy/<ipython console> in <module>()

 AttributeError: 'str' object has no attribute 'startwith'    是startswith

 In [25]: test_string.startswith('i')
 Out[25]: True

 In [26]: test_string.startswith('am')
 Out[26]: False

 In [27]: test_string.endswith('am')
 Out[27]: False

 In [28]: test_string.endswith('dent')
 Out[28]: True1.4 利用lstrip(),rstrip,strip依次删除前导空白，结尾空白，前后空白；空白可为tab，空格，回车，换行；不带参数使用时，可以返回新的字符串；
In [29]: test_string = "\n\t i am a student \n \t\r"

 In [30]: tes
 test2.py     test_string  

 In [30]: test_string
 Out[30]: '\n\t i am a student \n \t\r'

 In [31]: print te
 test2.py     test_string  

 In [31]: print test_string

      i am a student 
      

 In [32]: test_string.lstrip()
 Out[32]: 'i am a student \n \t\r'          去除前方空白

 In [33]: print test_string

      i am a student 
      

 In [34]: print test_string.lstrip()          去除前方空白
 i am a student 
      

 In [35]: print test_string.rstrip()             去除后方空白

      i am a student

 In [36]: test_string.rstrip()
 Out[36]: '\n\t i am a student'                   去除后方空白

 In [37]: test_string.strip()
 Out[37]: 'i am a student'                           去除前后空白

 In [38]: print test_string.strip()                      去除前后空白
 i am a student加参数时去除特定字符
如下：
In [39]: string = '< i am a student >'

 In [40]: str
 str     string  

 In [40]: string .lstrip("<")
 Out[40]: ' i am a student >'         删除前一个<

 In [41]: string .rstrip(">")
 Out[41]: '< i am a student '         删除后一个>

 In [42]: string .strip(">")
 Out[42]: '< i am a student '          删除后一个>In [43]: string .strip("<>")             
 Out[43]: ' i am a student '            删除<>

 In [44]: string .rstrip("<>")
 Out[44]: '< i am a student '

 In [45]: string .strip("<").strip(">")
 Out[45]: ' i am a student '                        删除<>

 In [46]: In [46]: string = '< i am <><>a student >'       重新赋值

 In [47]: string .rstrip("<>")
 Out[47]: '< i am <><>a student '

 In [48]: string .strip("<>")
 Out[48]: ' i am <><>a student '           但只能删除前后的In [49]: string = '<foooo> i am <fooo><>a student <foooo>'

 In [50]: string .strip("<>")
 Out[50]: 'foooo> i am <fooo><>a student <foooo'                     但只能删除前后的

 In [51]: string = '<foooo> i am <fooo><>a student <foooo>'

 In [52]: string .strip("<fo>")
 Out[52]: ' i am <fooo><>a student '                       只能删除前后的，但是删除了其它字符，说明没有按照输入字符的顺序进行匹配删除

 In [53]: 1.5 利用split 根据某个指定的分隔符对一个字符串进行提取
如：
n [53]: a = "i,am,a,student,from,china"

 In [54]: a.split(',')
 Out[54]: ['i', 'am', 'a', 'student', 'from', 'china']In [55]: a = "iFamFaFstudentFfromFchina"                 非分隔符，对某一字符或串也有效

 In [56]: a.split('F')
 Out[56]: ['i', 'am', 'a', 'student', 'from', 'china']             

1.6 连接多个字符串为一体In [57]: a = ['i' 'am' 'a' 'student' 'from' 'china']      列表

 In [58]: ' '.join(a)
 Out[58]: 'iamastudentfromchina'                   根据空格合并

 In [59]: '  '.join(a)
 Out[59]: 'iamastudentfromchina'

 In [60]: ''.join(a)
 Out[60]: 'iamastudentfromchina'

 In [61]: ' ,'.join(a)
 Out[61]: 'iamastudentfromchina'1.7替换某部分字符串
In [72]: test_string = "i am a student from china"

 In [73]: te
 test2.py     test_string  

 In [73]: test_string.replace("china","USA")
 Out[73]: 'i am a student from USA'

 以上是使用内建的字符串类型str 进行字符串处理。1.8 Unicode字符串
创建一个Unicode字符串
：
In [80]: u_string = u'this is a unicode string'              使用U 开头创建

 In [81]: u_string
 Out[81]: u'this is a unicode string'

 In [82]: print u_string
 this is a unicode string

 In [83]: unicode('this is a unicode string')                    使用unicode函数创建
 Out[83]: u'this is a unicode string'

 In [84]: a = unicode('this is a unicode string')            赋值  并输出

 In [85]: a
 Out[85]: u'this is a unicode string'

 In [86]: print a
 this is a unicode string