How do I add attributes to SubElement in ElementTree (Python)

Question

I successfully added a new node to an Element using PY's ElementTree. I now try to give it attributes, which fails, despite I'm following the tutorial.

my example xml:

<?xml version="1.0" encoding="UTF-8"?>
<xml>
<level01>
<level02>
<level03>
<level04>
<node q="3,4,5,7,8" p="zen"/>
<node q="a,s,e,o,l" p="zen"/>
</level04>
</level03>
# >> here will be the new node, called <subi/> <<   
<level03>
<level04>
<node q="x,y" p="zen"/>
<node q="xxx,yyy" p="zen"/>
</level04>
</level03>
</level02>
</level01>
</xml>

The node is created like this:

subi = ETL.SubElement(root[0][0][1][0][0], 'subi')

which works, it can then be accessed via root001000 and it's tag can be read.

but I fail trying to add attributes.

I tried using the syntax I found in another thread here: (with my names ofc)

>>> myattributes = {"size": "small", "gender": "unknown"}
>>> child = ET.SubElement(parent, "child", attrib=myattributes, age="10" )

Also I tried it directly, like

subi = ETL.SubElement(root[0][0][1][0][0], 'subi', attrib={"size": "small", "gender": "unknown"})

Results are always

root[0][0][1][0][0][0].tag
'subi'

but

root[0][0][1][0][0][0].attrib
{}

I also found how lxml does it, but this does not work with elementtree

#Any keyword arguments of the form name=value that you supply to the constructor are added #to the element's attributes. For example, this code:

newReed = etree.Element('reed', pitch='440', id='a4')

#will produce an element that looks like this:

<reed pitch='440' id='a4'/>

What am I doing wrong? How can I do it right? Is there a way to make elementtree do it? Or do I have to use lxml? (which would be dispreferred) ?

Answer 1

Isn't this you are trying to do? Assuming that subi is your element and you can access it, you can further use ElementTree method set:

subi.set(attr, value)

Look here about set method of ElementTree : https://docs.python.org/2/library/xml.etree.elementtree.html#xml.etree.ElementTree.Element.set

Answer 2

You can specify attributes for an Element or SubElement during creation with keyword arguments.

import xml.etree.ElementTree as ET

root = ET.Element('Summary')
ET.SubElement(root, 'TextSummary', Status='Completed')
# <Summary><TextSummary Status="Completed" /></Summary>

Alternatively, you can use .set to add an attribute to an element after creation.

import xml.etree.ElementTree as ET

root = ET.Element('Summary')
sub = ET.SubElement(root, 'TextSummary')
sub.set('Status', 'Completed')
# <Summary><TextSummary Status="Completed" /></Summary>

Generated XML:

<Summary>
    <TextSummary Status="Completed"/>
</Summary>

---

Explanation:

The constructors for Element and SubElement include **extra, which accepts attributes as keyword arguments.

xml.etree.ElementTree.Element(tag, attrib={}, **extra)
xml.etree.ElementTree.SubElement(parent, tag, attrib={}, **extra)

This allows you to add an arbitrary number of attributes.

root = ET.Element('Summary', Date='2018/07/02', Timestamp='11:44am')
# <Summary Date = "2018/07/02" Timestamp = "11:44am">

You can also use use .set to add attributes to a pre-existing element. However, this can only add one element at a time. (Suggested by German Petrov).

root = ET.Element('Summary')
root.set('Date', '2018/07/02')
root.set('Timestamp', '11:44am')
# <Summary Date = "2018/07/02" Timestamp = "11:44am">

---

Full Example:

import xml.etree.ElementTree as ET

root = ET.Element('school', name='Willow Creek High')
ET.SubElement(root, 'student', name='Jane Doe', grade='9')
print(ET.tostring(root).decode())
# <school name="Willow Creek High"><student grade="9" name="Jane Doe" /></school>