在解析的 XML 中忠实地保留注释

Question

我想在操作 XML 时尽可能忠实地保留 cmets。

我设法保留了 cmets，但内容被 XML 转义了。

#!/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，cmets 喜欢这样：

  <!--
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>
  -->

最终结果为：

  <!--
            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;
   -->

我也在CommentedTreeBuilder.py 中尝试了self._target.data( saxutils.unescape(data) )，但它似乎没有做任何事情。事实上，我认为问题发生在handle_commment() 步骤之后的某个地方。

顺便说一句，这个问题和this类似。

Answer 1

使用 Python 2.7 和 3.5 测试，以下代码应按预期工作。

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

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

然后，在主代码中使用

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

作为解析器而不是当前解析器。

顺便说一句，cmets 开箱即用，lxml 可以正常工作。也就是说，你可以这样做

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

以上都不需要。

Answer 2

Python 3.8 将insert_comments 参数添加到TreeBuilder，其中：

class xml.etree.ElementTree.TreeBuilder(element_factory=None, *, comment_factory=None, pi_factory=None, insert_comments=False, insert_pis=False)

当 insert_cmets 和/或 insert_pis 为真时，如果 cmets/pis 出现在根元素内（但不在根元素之外），它们将被插入到树中。

例子：

parser = ElementTree.XMLParser(target=ElementTree.TreeBuilder(insert_comments=True))

Answer 3

Martin 的代码对我不起作用。我修改了以下内容，按预期工作。

import xml.etree.ElementTree as ET

class CommentedTreeBuilder(ET.XMLTreeBuilder):
    def __init__(self, *args, **kwargs):
        super(CommentedTreeBuilder, self).__init__(*args, **kwargs)
        self._parser.CommentHandler = self.comment

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

这是测试

    parser=CommentedTreeBuilder()
    tree = ET.parse(filename, parser)
    tree.write('out.xml')

Answer 4

看起来@Martin 和@sukhbinder 的两个答案都对我不起作用...所以将其作为python 3.x 上可行的完整解决方案

from xml.etree import ElementTree

string = '''<?xml version="1.0"?>
<data>
    <!--Test
    -->
    <country name="Liechtenstein">
        <rank>1</rank>
        <year>2008</year>
        <gdppc>141100</gdppc>
        <neighbor name="Austria" direction="E"/>
        <neighbor name="Switzerland" direction="W"/>
    </country>
</data>'''

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

parser = ElementTree.XMLParser(target=CommentedTreeBuilder())
tree = ElementTree.fromstring(string, parser)
print(tree.find("./*[0]").text)
# or ElementTree.parse(filename, parser)

Answer 5

Martin 的回答是正确的，只是缺少一些代码， 我知道这对于更有经验的程序员来说可能是显而易见的，但作为一个新程序员，我花了一分钟才明白： 马丁的回答：

import xml.etree.ElementTree as ET
from xml.etree import ElementTree

class CommentedTreeBuilder(ElementTree.TreeBuilder):
# This class will retain remarks and comments oposed to the xml parser default
    def comment(self, data):
        self.start(ElementTree.Comment, {})
        self.data(data)
        self.end(ElementTree.Comment)

# the missing part:
def parse_xml_with_remarks(filepath):
    ctb = CommentedTreeBuilder()
    xp = ET.XMLParser(target=ctb)
    tree = ET.parse(filepath, parser=xp)
    return tree

# parsing the file, and getting root
tree=parse_xml_with_remarks(file)
root=tree.getroot()