Emitting namespace specifications with ElementTree in Python

Question

I am trying to emit an XML file with element-tree that contains an XML declaration and namespaces. Here is my sample code:

from xml.etree import ElementTree as ET ET.register_namespace('com',"http://www.company.com") #some name  # build a tree structure root = ET.Element("STUFF") body = ET.SubElement(root, "MORE_STUFF") body.text = "STUFF EVERYWHERE!"  # wrap it in an ElementTree instance, and save as XML tree = ET.ElementTree(root)  tree.write("page.xml",            xml_declaration=True,            method="xml" ) 

However, neither the <?xml tag comes out nor any namespace/prefix information. I'm more than a little confused here.

Answer 1

Although the docs say otherwise, I only was able to get an <?xml> declaration by specifying both the xml_declaration and the encoding.

You have to declare nodes in the namespace you've registered to get the namespace on the nodes in the file. Here's a fixed version of your code:

from xml.etree import ElementTree as ET ET.register_namespace('com',"http://www.company.com") #some name  # build a tree structure root = ET.Element("{http://www.company.com}STUFF") body = ET.SubElement(root, "{http://www.company.com}MORE_STUFF") body.text = "STUFF EVERYWHERE!"  # wrap it in an ElementTree instance, and save as XML tree = ET.ElementTree(root)  tree.write("page.xml",            xml_declaration=True,encoding='utf-8',            method="xml") 

Output (page.xml)

<?xml version='1.0' encoding='utf-8'?><com:STUFF xmlns:com="http://www.company.com"><com:MORE_STUFF>STUFF EVERYWHERE!</com:MORE_STUFF></com:STUFF> 

ElementTree doesn't pretty-print either. Here's pretty-printed output:

<?xml version='1.0' encoding='utf-8'?> <com:STUFF xmlns:com="http://www.company.com">     <com:MORE_STUFF>STUFF EVERYWHERE!</com:MORE_STUFF> </com:STUFF> 

---

You can also declare a default namespace and don't need to register one:

from xml.etree import ElementTree as ET  # build a tree structure root = ET.Element("{http://www.company.com}STUFF") body = ET.SubElement(root, "{http://www.company.com}MORE_STUFF") body.text = "STUFF EVERYWHERE!"  # wrap it in an ElementTree instance, and save as XML tree = ET.ElementTree(root)  tree.write("page.xml",            xml_declaration=True,encoding='utf-8',            method="xml",default_namespace='http://www.company.com') 

Output (pretty-print spacing is mine)

<?xml version='1.0' encoding='utf-8'?> <STUFF xmlns="http://www.company.com">     <MORE_STUFF>STUFF EVERYWHERE!</MORE_STUFF> </STUFF> 

Answer 2

I've never been able to get the <?xml tag out of the element tree libraries programatically so I'd suggest you try something like this.

from xml.etree import ElementTree as ET root = ET.Element("STUFF") root.set('com','http://www.company.com') body = ET.SubElement(root, "MORE_STUFF") body.text = "STUFF EVERYWHERE!"  f = open('page.xml', 'w') f.write('<?xml version="1.0" encoding="UTF-8"?>' + ET.tostring(root)) f.close() 

Non std lib python ElementTree implementations may have different ways to specify namespaces, so if you decide to move to lxml, the way you declare those will be different.