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[转] Python的转码

字符串内码的转换,是开发中经常遇到的问题。
在Java中,我们可以先对某个String调用getByte(),由结果生成新String的办法来转码,也可以用NIO包里面的Charset来实现
在Python中,可以对String调用decode和encode方法来实现转码。
比如,若要将某个String对象s从gbk内码转换为UTF-8,可以如下操作
s.decode('gbk').encode('utf-8')

可是,在实际开发中,我发现,这种办法经常会出现异常:
UnicodeDecodeError: 'gbk' codec can't decode bytes in position 30664-30665: illegal multibyte sequence

这 是因为遇到了非法字符——尤其是在某些用C/C++编写的程序中,全角空格往往有多种不同的实现方式,比如\xa3\xa0,或者\xa4\x57,这些 字符,看起来都是全角空格,但它们并不是“合法”的全角空格(真正的全角空格是\xa1\xa1),因此在转码的过程中出现了异常。

这样的问题很让人头疼,因为只要字符串中出现了一个非法字符,整个字符串——有时候,就是整篇文章——就都无法转码。

幸运的是,tiny找到了完美的解决办法(我因此被批评看文档不仔细,汗啊……)
s.decode('gbk', 'ignore').encode('utf-8')

因为decode的函数原型是decode([encoding], [errors='strict']),可以用第二个参数控制错误处理的策略,默认的参数就是strict,代表遇到非法字符时抛出异常;
如果设置为ignore,则会忽略非法字符;
如果设置为replace,则会用?取代非法字符;
如果设置为xmlcharrefreplace,则使用XML的字符引用。

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