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]: True

1.4 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