Is there a way to get a line number from an ElementTree Element

问题

So I'm parsing some XML files using Python 3.2.1's cElementTree, and during the parsing I noticed that some of the tags were missing attribute information. I was wondering if there is any easy way of getting the line numbers of those Elements in the xml file.

回答1:

Looking at the docs, I see no way to do this with cElementTree.

However I've had luck with lxmls version of the XML implementation. Its supposed to be almost a drop in replacement, using libxml2. And elements have a sourceline attribute. (As well as getting a lot of other XML features).

Only caveat is that I've only used it in python 2.x - not sure how/if it works under 3.x - but might be worth a look.

Addendum: from their front page they say :

The lxml XML toolkit is a Pythonic binding for the C libraries libxml2 and libxslt. It is unique in that it combines the speed and XML feature completeness of these libraries with the simplicity of a native Python API, mostly compatible but superior to the well-known ElementTree API. The latest release works with all CPython versions from 2.3 to 3.2. See the introduction for more information about background and goals of the lxml project. Some common questions are answered in the FAQ.

So it looks like python 3.x is OK.

回答2:

Took a while for me to work out how to do this using Python 3.x (using 3.3.2 here) so thought I would summarize:

# Force python XML parser not faster C accelerators
# because we can't hook the C implementation
sys.modules['_elementtree'] = None
import xml.etree.ElementTree as ET

class LineNumberingParser(ET.XMLParser):
    def _start_list(self, *args, **kwargs):
        # Here we assume the default XML parser which is expat
        # and copy its element position attributes into output Elements
        element = super(self.__class__, self)._start_list(*args, **kwargs)
        element._start_line_number = self.parser.CurrentLineNumber
        element._start_column_number = self.parser.CurrentColumnNumber
        element._start_byte_index = self.parser.CurrentByteIndex
        return element

    def _end(self, *args, **kwargs):
        element = super(self.__class__, self)._end(*args, **kwargs)
        element._end_line_number = self.parser.CurrentLineNumber
        element._end_column_number = self.parser.CurrentColumnNumber
        element._end_byte_index = self.parser.CurrentByteIndex
        return element

tree = ET.parse(filename, parser=LineNumberingParser())

回答3:

I've done this in elementtree by subclassing ElementTree.XMLTreeBuilder. Then where I have access to the self._parser (Expat) it has properties _parser.CurrentLineNumber and _parser.CurrentColumnNumber.

http://docs.python.org/py3k/library/pyexpat.html?highlight=xml.parser#xmlparser-objects has details about these attributes

During parsing you could print out info, or put these values into the output XML element attributes.

If your XML file includes additional XML files, you have to do some stuff that I don't remember and was not well documented to keep track of the current XML file.

回答4:

One (hackish) way of doing this is by inserting a dummy-attribute holding the line number into each element, before parsing. Here's how I did this with minidom:

python reporting line/column of origin of XML node

This can be trivially adjusted to cElementTree (or in fact any other python XML parser).

来源：https://stackoverflow.com/questions/6949395/is-there-a-way-to-get-a-line-number-from-an-elementtree-element

标签

python

xml

python-3.x

elementtree