Generate XML that uses a default namespace

Question

I want to use Python and lxml to generate XML like the following:

<root xmlns="foo">
  <bar />
</root>

However, the following code creates XML that is semantically identical, but uses ugly auto-generated namespace prefixes instead:

from lxml import etree
root = etree.Element('{foo}root')
etree.SubElement(root,'{foo}bar')
print(etree.tostring(root))
#=> b'<ns0:root xmlns:ns0="foo"><ns0:bar/></ns0:root>'

How do I get lxml/etree to generate XML using a single default namespace on the root element, with no namespace prefixes on any descendant elements?

@LutzHorn Perhaps I'm missing a sentence, but that tutorial (which I've read) only describes how to query against a default namespace, not how to get serialization to emit a default namespace. — Phrogz
– Phrogz, Commented Nov 1, 2016 at 18:44

user6999902 · Accepted Answer · 2016-11-01 18:48:11Z

4

Use the nsmap parameter, which is described on http://lxml.de/tutorial.html#namespaces

from lxml import etree

nsmap = {None: "foo"}
root = etree.Element('{foo}root', nsmap=nsmap)
etree.SubElement(root,'{foo}bar')
print(etree.tostring(root))

Output

b'<root xmlns="foo"><bar/></root>'

answered Nov 1, 2016 at 18:48

user6999902

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1 Comment

nogenius Over a year ago

This works in terms of the printed result, i.e. after serialization. However, is not quite correct. Actually giving the namespace explicitly does not look nice but is correct. For details see discussion here: github.com/lxml/lxml/pull/136

alecxe · Accepted Answer · 2016-11-01 18:47:29Z

3

The most straightforward approach would be to not use the namespaces as is, but set the xmlns attribute explicitly:

from lxml import etree

root = etree.Element('root')
root.attrib["xmlns"] = "foo"

etree.SubElement(root, 'bar')

print(etree.tostring(root))

Prints:

<root xmlns="foo"><bar/></root>

answered Nov 1, 2016 at 18:47

alecxe

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1 Comment

Phrogz Over a year ago

I probably won't accept this answer, because it's a dirty hack, but I will almost certainly end up using this answer in my code because it's a delightfully dirty hack.

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