Modify a XML using ElementTree

Question

<grandParent>
    <parent>
       <child>Sam/Astronaut</child>
    </parent>
</grandParent>

I want to modify the above XML by adding another child tag inside parent tag. I'm doing something like this..

tree = ET.parse("test.xml")
a=ET.Element('parent')
b=ET.SubElement(a,"child")
b.text="Jay/Doctor"
tree.write("test.xml")

Is this the correct way of modifying the xml file? Any better way? or what else should I be taking care of in the above code?

Answer 1

Your code creates a whole new tree and adds Jay to it. You need to connect Jay to the existing tree, not to a new one.

Try this:

import xml.etree.ElementTree as ET

tree = ET.parse("test.xml")
a = tree.find('parent')          # Get parent node from EXISTING tree
b = ET.SubElement(a,"child")
b.text = "Jay/Doctor"
tree.write("test.xml")

If you want to search for a particular child, you could do this:

import xml.etree.ElementTree as ET
tree = ET.parse("test.xml")
a = tree.find('parent')
for b in a.findall('child'):
    if b.text.strip() == 'Jay/Doctor':
        break
else:
    ET.SubElement(a,"child").text="Jay/Doctor"
tree.write("test.xml")

Notice a.findall() (similar to a.find(), but returns all of the named elements). xml.etree has very limited search criteria. You might consider using lxml.etree and its .xpath() method.