中文字符处理
str<---->unicode
从左到右是decode ,从右往左是encode
<type 'str'> ---><type 'unicode'>
decode('utf-8','gbk','gb2312')
<type 'unicode'> ---><type 'str'>
encode('utf-8','gbk','gb2312')
http://www.javashuo.com/article/p-hyjwwfsv-mu.html