Adding new element to a subtree using Element Tree

Question

I m struggling adding data to a subtree using ElementTree; my XML file looks like this:

Generally, I would use et.SubElement to add a new tag, but it will it write under "file" (i.e. = et.SubElement(tree.getroot(), 'new tag') and then I would add what I need using .text .attrib . etc etc ).

I would like to add another "instance" to the path: file/all_instances, which is the bit that I am struggling with.

In conclusion, there should be another "instance" under the subtree "all_instance", with the same structure (ID, Start, etc etc). So, my ideal output would be:

<instance>
    <ID> .. </ID>
    <start> ..</start>
    <end>.. </end>
    <code> ..</code>
</instance>

Thank you for your help :)

EDIT:

Here my XML file:

<file>
<SESSION_INFO>
<start_time>2016-11-24 02:58:34.36 -0800</start_time>
</SESSION_INFO>
<ALL_INSTANCES>
<instance>
<ID>1</ID>
<start>18.8426378227</start>
<end>71.6020237264</end>
<code>Shot </code>
</instance>
<instance>
<ID>2</ID>
<start>139.4355198883</start>
<end>199.7319609211</end>
<code>Shot </code>
<label>
<text>Succ</text>
</label>
</instance>
<instance>
<ID>3</ID>
<start>237.4172365666</start>
<end>305.2507327285</end>
<code>Shot </code>
</instance>


</ALL_INSTANCES>

<ROWS>
<row>
<code>Shot </code>
<R>57000</R>
<G>57000</G>
<B>57000</B>
</row>
<row>
<code>Shot Succ</code>
<R>57000</R>
<G>57000</G>
<B>57000</B>
</row>
</ROWS>
</file>

What exactly are you struggling with? It is not clear. Show us code and XML markup: please provide a minimal reproducible example. — mzjn
– mzjn, Commented Nov 21, 2019 at 13:05

Daniel Haley · Accepted Answer · 2019-11-21 19:14:41Z

Instead of using:

et.SubElement(tree.getroot(), 'instance')

you could use:

et.SubElement(tree.find("./ALL_INSTANCES"), 'instance')

You could also build up your new instance element structure as a string first then turn it into an Element and either append() or insert() it into ALL_INSTANCES.

Example...

import xml.etree.ElementTree as ET

tree = ET.parse("input.xml")

new_instance = """<instance>
<ID> .. </ID>
<start> .. </start>
<end> .. </end>
<code> .. </code>
</instance>
"""

tree.find("./ALL_INSTANCES").append(ET.fromstring(new_instance))

print(ET.tostring(tree.getroot()).decode())

prints...

<file>
<SESSION_INFO>
<start_time>2016-11-24 02:58:34.36 -0800</start_time>
</SESSION_INFO>
<ALL_INSTANCES>
<instance>
<ID>1</ID>
<start>18.8426378227</start>
<end>71.6020237264</end>
<code>Shot </code>
</instance>
<instance>
<ID>2</ID>
<start>139.4355198883</start>
<end>199.7319609211</end>
<code>Shot </code>
<label>
<text>Succ</text>
</label>
</instance>
<instance>
<ID>3</ID>
<start>237.4172365666</start>
<end>305.2507327285</end>
<code>Shot </code>
</instance>
<instance>
<ID> .. </ID>
<start> .. </start>
<end> .. </end>
<code> .. </code>
</instance></ALL_INSTANCES>
<ROWS>
<row>
<code>Shot </code>
<R>57000</R>
<G>57000</G>
<B>57000</B>
</row>
<row>
<code>Shot Succ</code>
<R>57000</R>
<G>57000</G>
<B>57000</B>
</row>
</ROWS>
</file>

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