编码还是编码

linix下用iconv可以来转换编码，实际中还是有可能出错。

某个文本，从mysql的latin1表中导出，使用gb18030解码转成utf8，如果转换失败，就对失败的字符换成latin1进行转：

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#!/usr/local/python/bin/python
#-*- encoding: utf-8 -*-

import traceback,sys,re

fh=open('1.out','rb')
ofh=open('1.out.1','wb')


class MyException(Exception):
    def __init__(self,code,msg):
        self.args=(code,msg)
       
class NoPositionError(MyException):
    pass

class NotUnicodeError(MyException):
    pass   

def decodestr(todostr):
    global i #无法转换时记录下行数
    try:
        newstr=todostr.decode('gb18030').encode('utf8')
        return newstr
    except:
        t,v,tb=sys.exc_info()
        errstr=traceback.format_exception_only(t,v)[0]  
        print i    
        if errstr.startswith('UnicodeDecodeError'):
            m=re.search(r'position (\d+)[:|-]',errstr)
            if m:
              redoint=int(m.group(1))
              newstr_left=todostr[:redoint].decode('18030').encode('utf8')
              newstr_mid=todostr[redoint].decode('latin_1').encode('utf8')
              newstr_right=decodestr(todostr[redoint+1:])
              newstr = newstr_left+newstr_mid+newstr_right
              return newstr
            else:
              raise NoPositionError('',errstr)
        else:  raise    NotUnicodeError('',newstr)

i=0
while 1:
    i=i+1
    l=fh.readline()
    if l:
        l=l.strip()
        nl=decodestr(l)
        print >>ofh,nl
    else: break

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