Python学习笔记3-字符串

格式化字符串／复合字段名

>>> import humansize

>>> si_suffixes = humansize.SUFFIXES[1000]

>>> si_suffixes

['KB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB']





>>> '1000{0[0]} = 1{0[1]}'.format(si_suffixes)

'1000KB = 1MB'

 

>>> import humansize

>>> import sys

>>> '1MB = 1000{0.modules[humansize].SUFFIXES[1000][0]}'.format(sys)

'1MB = 1000KB'

 

Sys.modules 是一个保存当前python实例中搜有已导入模块的字典。模块的名字为键，模块自身为值。

 

 



>>> s = '''finished files are the re-



sults of years of scientific study combined with the



experience of years. ‘''



 



>>> s.splitlines()



['finished files are the re-', 'sults of years of scientific study combined with the', 'experience of years. ‘]



 



>>> print(s.lower())



finished files are the re-



sults of years of scientific study combined with the



experience of years. 

 

 

 



>>> a_list = query.split("&")



>>> a_list



['user=pilgrim', 'database=master', ‘password=PapayaWhip']



 



>>> a_list_of_list = [v.split('=',1) for v in a_list]



>>> a_list_of_list



[['user', 'pilgrim'], ['database', 'master'], ['password', ‘PapayaWhip']]



 



>>> a_dict = dict(a_list_of_list)



>>> a_dict



{'password': 'PapayaWhip', 'database': 'master', 'user': ‘pilgrim'}

  

split()－根据指定的分隔符，将字符串分隔成一个字符串列表。

dict() － 将包含列表的列表转换成字典对象

 

 

字符串的分片

 

>>> a_string = "My alphabet starts where your alphabet ends."



>>> a_string[3:11]



‘alphabet'



 



>>> a_string[3:-3]



'alphabet starts where your alphabet en’



 



>>> a_string[:18]



'My alphabet starts’



 



>>> a_string[18:]



' where your alphabet ends.'

 

 

String VS. Bytes

 

Bytes对象的定义：b’ ’, eg: by = b’abcd\x65’

Bytes对象不能改变其值，但可以通过内置函数bytearry()将bytes对象转化成bytearry对象，bytearry对象的值可改变

 

 



>>> by = b'abcd\x65'



>>> barr = bytearray(by)



>>> barr



bytearray(b'abcde')



 



>>> barr[0]=102



>>> barr



bytearray(b'fbcde')



 

 

>>> a_string = "dive into python"



>>> by = a_string.encode('utf-8')

>>> by

b'dive into python'



>>> roundtrip = by.decode('big5')

>>> roundtrip

'dive into python'

 

string.encode() -- 使用某种编码方式作为参数，将字符串转化为bytes对象。

bytes.decode() -- 使用某种编码方式作为参数，将bytes对象转化成字符串对象。