etree_example2.py

# Related to https://gist.github.com/nakagami/b822ad3fcb72645f003e639060586be9
# Retain the first element, delete the rest.
# modify attribute
# modify element

import xml.etree.ElementTree as ET

xml_data = '''<?xml version="1.0" encoding="utf-8"?>
<root>
    <person id="1">
        <name>John Doe</name>
        <age>30</age>
        <city>Tokyo</city>
    </person>
    <person id="2">
        <name>Jane Smith</name>
        <age>25</age>
        <city>New York</city>
    </person>
</root>
'''

root = ET.fromstring(xml_data)

for i, person in enumerate(root.iter("person")):
    if i == 0:
        person.set("id", "100")
        name = person.find("name")
        name.text = 'John Doe Jr.'
        age = person.find('age')
        age.text = '31'
    else:
        root.remove(person)

edited_xml = ET.tostring(root, encoding='utf-8', method='xml', xml_declaration=True).decode('utf-8')
print(edited_xml)