How can i do replace a child element(s) in ElementTree

Question

I want to replace child elements from one tree to another , based on some criteria. I can do this using Comprehension ? But how do we replace element in ElementTree?

Hanghangar

This might help: https://mcmap.net/q/1156361/-insert-a-node-for-an-element-in-xml-with-python-elementtree/535275 – Herbst

Answer 1

You can't replace an element from the ElementTree you can only work with Element.

Even when you call ElementTree.find() it's just a shortcut for getroot().find().

So you really need to:

• extract the parent element
• use comprehension (or whatever you like) on that parent element

The extraction of the parent element can be easy if your target is a root sub-element (just call getroot()) otherwise you'll have to find it.

Wrinkly

Answer 2

Unlike the DOM, etree has no explicit multi-document functions. However, you should be able to just move elements freely from one document to another. You may want to call _setroot after doing so.

By calling insert and then remove, you can replace a node in a document.

Gland

Answer 3

I'm new to python, but I've found a dodgy way to do this:

Input file input1.xml:

<?xml version="1.0" encoding="UTF-8"?>
<root>
    <import ref="input2.xml" />
    <name awesome="true">Chuck</name>
</root>

Input file input2.xml:

<?xml version="1.0" encoding="UTF-8"?>
<foo>
    <bar>blah blah</bar>
</foo>

Python code: (note, messy and hacky)

import os
import xml.etree.ElementTree as ElementTree

def getElementTree(xmlFile):
    print "-- Processing file: '%s' in: '%s'" %(xmlFile, os.getcwd())
    xmlFH = open(xmlFile, 'r')
    xmlStr = xmlFH.read()
    et = ElementTree.fromstring(xmlStr)
    parent_map = dict((c, p) for p in et.getiterator() for c in p)
    # ref: https://mcmap.net/q/234774/-access-elementtree-node-parent-node/2170994
    importList = et.findall('.//import[@ref]')
    for importPlaceholder in importList:
        old_dir = os.getcwd()
        new_dir = os.path.dirname(importPlaceholder.attrib['ref'])
        shallPushd = os.path.exists(new_dir)
        if shallPushd:
            print "  pushd: %s" %(new_dir)
            os.chdir(new_dir) # pushd (for relative linking)
        # Recursing to import element from file reference
        importedElement = getElementTree(os.path.basename(importPlaceholder.attrib['ref']))

        # element replacement
        parent = parent_map[importPlaceholder]
        index = parent._children.index(importPlaceholder)
        parent._children[index] = importedElement

        if shallPushd:
            print "  popd: %s" %(old_dir)
            os.chdir(old_dir) # popd

    return et

xmlET = getElementTree("input1.xml")
print ElementTree.tostring(xmlET)

gives the output:

-- Processing file: 'input1.xml' in: 'C:\temp\testing'
-- Processing file: 'input2.xml' in: 'C:\temp\testing'
<root>
    <foo>
    <bar>blah blah</bar>
</foo><name awesome="true">Chuck</name>
</root>

this was concluded with information from:

• stackoverflow answer: access ElementTree node parent node
• accessing parents from effbot.org

Ligneous

Answer 4

Yes! Using the slice syntax you can do it with comprehension. Ex:

import xml.etree.ElementTree as etree

path = r'C:\Users\XXX\myfile.xml'
tree = etree.parse(path)
root = tree.getroot()


root[:] = [child for child in root if child.get('some-attribute') == 'something']
tree.write(f'{path}.filtered.xml')

Memphis