在Parsed XML中保留注释（Python 2.7）

Question

我想在操作XML时尽可能忠实地保留注释。

我设法保留评论，但内容得到XML转义。

#!/usr/bin/env python 
# add_host_to_tomcat.py 

import xml.etree.ElementTree as ET 
from CommentedTreeBuilder import CommentedTreeBuilder 
parser = CommentedTreeBuilder() 

if __name__ == '__main__': 
    filename = "/opt/lucee/tomcat/conf/server.xml" 

    # this is the important part: use the comment-preserving parser 
    tree = ET.parse(filename, parser) 

    # get the node to add a child to 
    engine_node = tree.find("./Service/Engine") 

    # add a node: Engine.Host 
    host_node = ET.SubElement(
     engine_node, 
     "Host", 
     name="local.mysite.com", 
     appBase="webapps" 
    ) 
    # add a child to new node: Engine.Host.Context 
    ET.SubElement(
     host_node, 
     'Context', 
     path="", 
     docBase="/path/to/doc/base" 
    ) 

    tree.write('out.xml') 

#!/usr/bin/env python 
# CommentedTreeBuilder.py 

from xml.etree import ElementTree 

class CommentedTreeBuilder (ElementTree.XMLTreeBuilder): 
    def __init__ (self, html = 0, target = None): 
     ElementTree.XMLTreeBuilder.__init__(self, html, target) 
     self._parser.CommentHandler = self.handle_comment 

    def handle_comment (self, data): 
     self._target.start(ElementTree.Comment, {}) 
     self._target.data(data) 
     self._target.end(ElementTree.Comment) 

然而，像这样的评论：

<!-- 
EXAMPLE HOST ENTRY: 
    <Host name="lucee.org" appBase="webapps"> 
     <Context path="" docBase="/var/sites/getrailo.org" /> 
    <Alias>www.lucee.org</Alias> 
    <Alias>my.lucee.org</Alias> 
    </Host> 

HOST ENTRY TEMPLATE: 
    <Host name="[ENTER DOMAIN NAME]" appBase="webapps"> 
     <Context path="" docBase="[ENTER SYSTEM PATH]" /> 
    <Alias>[ENTER DOMAIN ALIAS]</Alias> 
    </Host> 
    --> 

最终成为：

<!-- 
      EXAMPLE HOST ENTRY: 
    &lt;Host name="lucee.org" appBase="webapps"&gt; 
     &lt;Context path="" docBase="/var/sites/getrailo.org" /&gt; 
     &lt;Alias&gt;www.lucee.org&lt;/Alias&gt; 
     &lt;Alias&gt;my.lucee.org&lt;/Alias&gt; 
    &lt;/Host&gt; 

    HOST ENTRY TEMPLATE: 
    &lt;Host name="[ENTER DOMAIN NAME]" appBase="webapps"&gt; 
     &lt;Context path="" docBase="[ENTER SYSTEM PATH]" /&gt; 
     &lt;Alias&gt;[ENTER DOMAIN ALIAS]&lt;/Alias&gt; 
    &lt;/Host&gt; 
    --> 

我也试过CommentedTreeBuilder.pyself._target.data(saxutils.unescape(data))，但它似乎并没有做任何事情。事实上，我认为问题发生在handle_commment()之后的某个地方。

顺便提一下，这个问题类似于this。

Answer 1

经过Python 2.7和3.5的测试，下面的代码应该按预期工作。

#!/usr/bin/env python 
# CommentedTreeBuilder.py 
from xml.etree import ElementTree 

class CommentedTreeBuilder(ElementTree.TreeBuilder): 
    def __init__(self, *args, **kwargs): 
     super(CommentedTreeBuilder, self).__init__(*args, **kwargs) 

    def comment(self, data): 
     self.start(ElementTree.Comment, {}) 
     self.data(data) 
     self.end(ElementTree.Comment) 

然后，在主代码使用

parser = ET.XMLParser(target=CommentedTreeBuilder()) 

作为解析器，而不是当前的。

顺便说一下，注释与lxml开箱即可正常使用。也就是说，你可以做

import lxml.etree as ET 
tree = ET.parse(filename) 

不需要任何上述。