python+expat:实体出错

我编写了一个小函数,它使用elementtree和xpath提取XML文件中某些元素的文本内容:

#!/usr/bin/env python2.5

import doctest
from xml.etree import ElementTree
from StringIO import StringIO

def parse_xml_etree(sin, xpath):
  """
Takes as input a stream containing XML and an XPath expression.
Applies the XPath expression to the XML and returns a generator
yielding the text contents of each element returned.

>>> parse_xml_etree(
...   StringIO('<test><elem1>one</elem1><elem2>two</elem2></test>'),
...   '//elem1').next()
'one'
>>> parse_xml_etree(
...   StringIO('<test><elem1>one</elem1><elem2>two</elem2></test>'),
...   '//elem2').next()
'two'
>>> parse_xml_etree(
...   StringIO('<test><null>&#0;</null><elem3>three</elem3></test>'),
...   '//elem2').next()
'three'
"""

  tree = ElementTree.parse(sin)
  for element in tree.findall(xpath):
    yield element.text  

if __name__ == '__main__':
  doctest.testmod(verbose=True)

第三次测试失败,但出现以下异常:

expatError:对无效字符号的引用:第1行第13列

是 � 实体非法XML?不管它是不是,我想要解析的文件都包含它,我需要某种方法来解析它们。除了expat,还有其他解析器的建议,或者expat的设置,可以让我这样做吗?

更新:我发现 BeautifulSoup 刚才,在回答注释中有一个如下所述的标签汤解析器,为了好玩,我回到这个问题,尝试将它用作elementtree前面的XML清理器,但它尽职地转换了 &α0; 变成一个同样无效的空字节。-)

cleaned_s = StringIO(
  BeautifulStoneSoup('<test><null>&#0;</null><elem3>three</elem3></test>',
                     convertEntities=BeautifulStoneSoup.XML_ENTITIES
  ).renderContents()
)
tree = ElementTree.parse(cleaned_s)

…产量

xml.parsers.expat.ExpatError: not well-formed (invalid token): line 1, column 12

不过,在我的特殊情况下,我并不需要这样的xpath解析,我可以使用漂亮的soup本身及其非常简单的节点寻址风格。 parsed_tree.test.elem1.contents[0] .