How do I remove child node from XML in Python?

Question

I have a list of nodes which i would like to remove from a xml document. But i am running into a issue while removing the elements and writing the modified document into a new xml file.

Here is a python program i wrote [I am using elementTree]

from xml.etree.ElementTree import ElementTree
    tree = ElementTree()
    tree.parse('autogen_test.xml')
    root = tree.getroot()
    keeper_data = ['4294905264']
    instances = tree.findall('./DIMENSION/DIMENSION_NODE/DIMENSION_NODE')
    removeList = list()
    for instance in instances:
        #print instance
        data1 = instance.find('./DVAL/DVAL_ID')
        if data1.attrib.get("ID") not in keeper_data:
            removeList.append(instance)
    for tag in removeList:
        parent = tree.findall('./DIMENSION/DIMENSION_NODE/DIMENSION_NODE')
        parent.remove(tag)    
tree.write("out.xml")

My sample xml is as below [this is a standard input and i cannot modify it]

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE DIMENSIONS SYSTEM "dimensions.dtd">
<DIMENSIONS>
   <NUM_DVALS>88816</NUM_DVALS>
   <DIMENSION NAME="Brand" SRC_FILE="" SRC_TYPE="INTERNAL">
      <DIMENSION_ID ID="4294905334"/>
      <DIMENSION_NODE>
         <DVAL TYPE="EXACT">
            <DVAL_ID ID="2"/>
            <SYN DISPLAY="TRUE" SEARCH="FALSE" CLASSIFY="FALSE">Brand</SYN>
         </DVAL>
         <DIMENSION_NODE>
            <DVAL TYPE="EXACT">
               <DVAL_ID ID="4294905325"/>
               <SYN DISPLAY="TRUE" SEARCH="TRUE" CLASSIFY="TRUE">hanes</SYN>
            </DVAL>
         </DIMENSION_NODE>
         <DIMENSION_NODE>
            <DVAL TYPE="EXACT">
               <DVAL_ID ID="4294905315"/>
               <SYN DISPLAY="TRUE" SEARCH="TRUE" CLASSIFY="TRUE">lee</SYN>
            </DVAL>
         </DIMENSION_NODE>
         <DIMENSION_NODE>
            <DVAL TYPE="EXACT">
               <DVAL_ID ID="4294905281"/>
               <SYN DISPLAY="TRUE" SEARCH="TRUE" CLASSIFY="TRUE">levi's</SYN>
            </DVAL>
         </DIMENSION_NODE>
         <DIMENSION_NODE>
            <DVAL TYPE="EXACT">
               <DVAL_ID ID="4294905264"/>
               <SYN DISPLAY="TRUE" SEARCH="TRUE" CLASSIFY="TRUE">braun</SYN>
            </DVAL>
         </DIMENSION_NODE>
        </DIMENSION_NODE>
   </DIMENSION>
   </DIMENSIONS>

Even after iterating through the list and finding all the node to remove. The tree.write("out.xml") always prints out the original xml. Basically i will need to remove the identified from the original xml.

Expected Output:

<DIMENSIONS>
   <NUM_DVALS>88816</NUM_DVALS>
   <DIMENSION NAME="Brand" SRC_FILE="" SRC_TYPE="INTERNAL">
      <DIMENSION_ID ID="4294905334" />
         <DIMENSION_NODE>
            <DVAL TYPE="EXACT">
               <DVAL_ID ID="4294905264" />
               <SYN CLASSIFY="TRUE" DISPLAY="TRUE" SEARCH="TRUE">braun</SYN>
            </DVAL>
         </DIMENSION_NODE>
        </DIMENSION_NODE>
   </DIMENSION>
   </DIMENSIONS>

@Noelkd tnx .. I editied the code to define the parent node. But i still run into same issue. — Ritwik Anburmath
– Ritwik Anburmath, Commented Jul 22, 2015 at 22:32
Indentation is broken now :( As far as I can understand you're trying to get the data about node 4294905264? — Noelkd
– Noelkd, Commented Jul 22, 2015 at 23:33

har07 · Accepted Answer · 2015-07-23 05:58:46Z

All DIMENSION_NODEs to be deleted share the same parent DIMENSION_NODE, so it would be more efficient to get it only once before looping through the removeList. More importantly, you want to get parent DIMENSION_NODE instead of the child DIMENSION_NODE, so the correct XPath for that is ./DIMENSION/DIMENSION_NODE. In short, try to change your 2nd for loop with the following codes :

parent = tree.find('./DIMENSION/DIMENSION_NODE')
for tag in removeList:
    parent.remove(tag)

This is full working example for demo (only need to replace source value with the actual XML) :

import xml.etree.ElementTree as ET

source = """replace with the XML in question"""

root = ET.fromstring(source)
keeper_data = ['4294905264']
instances = root.findall('.//DIMENSION/DIMENSION_NODE/DIMENSION_NODE')
removeList = list()
for instance in instances:
    data1 = instance.find('./DVAL/DVAL_ID')
    if data1.attrib.get("ID") not in keeper_data:
        removeList.append(instance)
parent = root.find('.//DIMENSION/DIMENSION_NODE')
for tag in removeList:
    parent.remove(tag)

print(ET.tostring(root))

given XML in question as value of source variable, the output is :

<DIMENSIONS>
   <NUM_DVALS>88816</NUM_DVALS>
   <DIMENSION NAME="Brand" SRC_FILE="" SRC_TYPE="INTERNAL">
      <DIMENSION_ID ID="4294905334" />
      <DIMENSION_NODE>
         <DVAL TYPE="EXACT">
            <DVAL_ID ID="2" />
            <SYN CLASSIFY="FALSE" DISPLAY="TRUE" SEARCH="FALSE">Brand</SYN>
         </DVAL>
         <DIMENSION_NODE>
            <DVAL TYPE="EXACT">
               <DVAL_ID ID="4294905264" />
               <SYN CLASSIFY="TRUE" DISPLAY="TRUE" SEARCH="TRUE">braun</SYN>
            </DVAL>
         </DIMENSION_NODE>
        </DIMENSION_NODE>
   </DIMENSION>
</DIMENSIONS>

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