Python xml.dom.minidom生成无效的XML？

Question

我遇到了一个奇怪的问题，跟python的xml.dom.minidom这个包有关。我生成了一个文档，并用从终端获取的数据填充它。有时候，这些数据里会包含一些终端控制字符。当我用minidom.toprettyxml()把这些字符存储到文本数据节点时，一切看起来都没问题，但生成的文档却不是一个有效的XML。

有没有人知道为什么minidom会允许生成无效的文档？这和“mini”这个词有关系吗？

下面是提取的示例代码（还有一些系统信息）：

Python 2.6.5 (r265:79063, Apr 16 2010, 13:57:41) 
[GCC 4.4.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from xml.dom import minidom
>>> impl = minidom.getDOMImplementation()
>>> doc = impl.createDocument(None, "results", None)
>>> root = doc.firstChild
>>> outString = "test "+chr(1) #here goes control character
>>> root.appendChild(doc.createTextNode(outString))
<DOM Text node "'test \x01'">
>>> doc.toprettyxml(encoding="utf-8")
'<?xml version="1.0" encoding="utf-8"?>\n<results>\n\ttest \x01\n</results>\n'
>>> with open("/tmp/outfile", "w") as f:
...     f.write(doc.toprettyxml(encoding="utf-8"))
... 
>>> doc2 = minidom.parse("/tmp/outfile")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.6/xml/dom/minidom.py", line 1918, in parse
    return expatbuilder.parse(file)
  File "/usr/lib/python2.6/xml/dom/expatbuilder.py", line 924, in parse
    result = builder.parseFile(fp)
  File "/usr/lib/python2.6/xml/dom/expatbuilder.py", line 207, in parseFile
    parser.Parse(buffer, 0)
xml.parsers.expat.ExpatError: not well-formed (invalid token): line 3, column 6
>>> open("/tmp/outfile","r").readlines()
['<?xml version="1.0" encoding="utf-8"?>\n', '<results>\n', '\ttest \x01\n', '</results>\n']
>>> 

Answer 1

看一下 _write_data 这个代码，它只处理了&符号、斜杠和括号：

def _write_data(writer, data):
    "Writes datachars to writer."
    data = data.replace("&", "&amp;").replace("<", "&lt;")
    data = data.replace("\"", "&quot;").replace(">", "&gt;")
    writer.write(data)

正如你猜测的，minidom 并不是一个非常强大的实现（比如它对命名空间的处理就不太完善）。