对于unicode代码点，python xml.etree.ElementTree tostring（）fromstring（）往返失败

Question

我在Python2.7中使用xml.etree.ElementTree，往返字符串时遇到问题。如果树中存在非ascii Unicode字符，则对ET.tostring()调用ET.fromstring()失败。

为什么这不管用？既然ElementTree想要bytestreams并进行自己的解码，那么为什么它默认为ASCII解析器？这是由我忽略的东西决定的吗，比如python文件的编码或语言环境？

1. 仅限ASCII字符：

   import xml.etree.ElementTree as ET
   
   t1 = ET.Element('test')
   t1.text = u'hello world'
   t1_roundtrip = ET.fromstring(ET.tostring(t1, encoding='utf8', method='xml'))
   # ET.dump(t1) == ET.dump(t1_roundtrip)
   

2. Unicode代码点失败：

   import xml.etree.ElementTree as ET
   
   t2 = ET.Element('test')
   t2.text = u'\u2603'
   t2_roundtrip = ET.fromstring(ET.tostring(t2, encoding='utf8', method='xml'))
   
   >>> t2_roundtrip = ET.fromstring(ET.tostring(t2, encoding='utf8', method='xml'))
   Traceback (most recent call last):
     File "<stdin>", line 1, in <module>
     File "/opt/rh/python27/root/usr/lib64/python2.7/xml/etree/ElementTree.py", line 1300, in XML
       parser.feed(text)
     File "/opt/rh/python27/root/usr/lib64/python2.7/xml/etree/ElementTree.py", line 1642, in feed
       self._raiseerror(v)
     File "/opt/rh/python27/root/usr/lib64/python2.7/xml/etree/ElementTree.py", line 1506, in _raiseerror
       raise err
   xml.etree.ElementTree.ParseError: not well-formed (invalid token): line 2, column 6