Faithfully Preserve Comments in Parsed XML

Tested with Python 2.7 and 3.5, the following code should work as intended.

#!/usr/bin/env python# CommentedTreeBuilder.pyfrom xml.etree import ElementTreeclass CommentedTreeBuilder(ElementTree.TreeBuilder):    def comment(self, data):        self.start(ElementTree.Comment, {})        self.data(data)        self.end(ElementTree.Comment)

Then, in the main code use

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

as the parser instead of the current one.

By the way, comments work correctly out of the box with lxml. That is, you can just do

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

without needing any of the above.

Python 3.8 added the insert_comments argument to TreeBuilder which:

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

When insert_comments and/or insert_pis is true, comments/pis will be inserted into the tree if they appear within the root element (but not outside of it).

Example:

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

Martin's Code didn't work for me. I modified the same with the following which works as intended.

import xml.etree.ElementTree as ETclass 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)

This is the test

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