How do I set attributes for an XML element with Python?

Question

I am using ElementTree to build an XML file.

When I try to set an element's attribute with ET.SubElement().__setattr__(), I get the error AttributeError: __setattr__.

import xml.etree.cElementTree as ET
summary = open(Summary.xml, 'w')
root = ET.Element('Summary')
ET.SubElement(root, 'TextSummary')
ET.SubElement(root,'TextSummary').__setattr__('Status','Completed') # Error occurs here
tree = ET.ElementTree(root) 
tree.write(summary)
summary.close()

After code execution, my XML should resemble the following:

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

How do I add attributes to an XML element with Python using xml.etree.cElementTree?

Answer 1

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')

XML:

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

---

Alternatively, you can use .set to add attributes to an existing element.

import xml.etree.ElementTree as ET

root = ET.Element('Summary')
sub = ET.SubElement(root, 'TextSummary')
sub.set('Status', 'Completed')

XML:

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

---

Technical 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. (As suggested by Thomas Orozco).

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>