python2 unicode str

Love The Way You Lie 2022-07-12 00:29 147阅读 0赞

# unicode #

unicode是一种编码方案， utf-8是unicode的一种实现方式。

# Python2 编码 #

In [1]: a = '啊哈哈'
    In [2]: a
    Out[2]: '\xe5\x95\x8a\xe5\x93\x88\xe5\x93\x88'
    In [4]: type(a)
    Out[4]: str
    In [5]: len(a)
    Out[5]: 9
    In [6]: b = u'姚赫赫'
    In [7]: type(b)
    Out[7]: unicode
    In [8]: len(b)
    Out[8]: 3
    In [9]: a.decode('utf-8')
    Out[9]: u'\u554a\u54c8\u54c8'
    In [10]: b
    Out[10]: u'\u59da\u8d6b\u8d6b'
    
    In [11]: b.encode('utf-8')
    Out[11]: '\xe5\xa7\x9a\xe8\xb5\xab\xe8\xb5\xab'
    
    In [12]: c = '姚赫赫'
    
    In [13]: c
    Out[13]: '\xe5\xa7\x9a\xe8\xb5\xab\xe8\xb5\xab'
    
    In [14]: import sys
    
    In [15]: sys.getdefaultencoding()
    Out[15]: 'ascii'
    
    In [16]: b + c
    ---------------------------------------------------------------------------
    UnicodeDecodeError                        Traceback (most recent call last)
    <ipython-input-16-c6b7c7e5694f> in <module>()
    ----> 1 b + c
    
    UnicodeDecodeError: 'ascii' codec can't decode byte 0xe5 in position 0: ordinal not in range(128) In [17]: import sys In [18]: relaod(sys) --------------------------------------------------------------------------- NameError Traceback (most recent call last) <ipython-input-18-f73449e725b6> in <module>() ----> 1 relaod(sys) NameError: name 'relaod' is not defined In [19]: reload(sys) <module 'sys' (built-in)> In [20]: sys.setdefaultencoding('utf-8') In [21]: b + c Out[21]: u'\u59da\u8d6b\u8d6b\u59da\u8d6b\u8d6b' In [22]: type(b + c) Out[22]: unicode

python2 中`a='啊哈哈'`, a的类型是str, 是编码后的字节序列。a的长度是字节数；而b的类型是unicode(存储文本字符串), b的长度是字符数。

## 相互转化 ##

str –>decode(‘utf-8’) –> unicode  
unicode –>encode(‘utf-8’)–> str  
写入文件的时候str类型的可以直接写入，unicode类型的必须encode之后写入。