Namespaces in lxml

Question

I want to create the following XML with lxml package:

<configuration xmlns:cond="http://www.aaa.com/orc/condition" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../schema/variation-config.xsd">
   <strategy id="XXX">
       <conditions>
          <cond:scenario>A</cond:scenario>
       </conditions>
   </strategy>
</configuration>

So far, I have the following code, which is not satisfactory at all:

XHTML_NAMESPACE = "http://www.aaa.com/orc/condition"
XHTML = "{%s}" % XHTML_NAMESPACE
NSMAP = {
    'cond' : XHTML_NAMESPACE,
    'xsi': 'http://www.w3.org/2001/XMLSchema-instance'
}
root = etree.Element(
    "configuration",
    nsmap=NSMAP,
)
strategy = etree.SubElement(root, "strategy", id="XXX")
conditions = etree.SubElement(strategy, "conditions")
cond1 = etree.SubElement(conditions, XHTML + "scenario", nsmap=NSMAP)
cond1.text = "A"

It gives me that:

<configuration xmlns:cond="http://www.aaa.com/orc/condition" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <strategy id="XXX">
    <conditions>
      <cond:scenario>A</cond:scenario>
    </conditions>
  </strategy>
</configuration>

Question:

I just miss the xsi:noNamespaceSchemaLocation="../schema/variation-config.xsd" . Do you know how I could add that to the XML?

Answer 1

After you updated your question with a better solution, I think you are missing a way to set an attribute for an existing element. Use the set method:

root.set(XSI + "noNamespaceSchemaLocation", "../schema/variation-config.xsd")

Also, when you add a subelement to an element that already knows namespaces defined in nsmap , there is no need to include nsmap again. In other words, instead of

cond1 = etree.SubElement(conditions, XHTML + "scenario", nsmap=NSMAP)

you can write

cond1 = etree.SubElement(conditions, XHTML + "scenario")

Finally, XHTML is an unfortunate variable name, since XHTML is a standard namespace.

Solution that produces the correct result

from lxml import etree

COND_NAMESPACE = "http://www.aaa.com/orc/condition"
XSI_NAMESPACE = "http://www.w3.org/2001/XMLSchema-instance"

COND = "{%s}" % COND_NAMESPACE
XSI = "{%s}" % XSI_NAMESPACE

nsmap = {"cond": "http://www.aaa.com/orc/condition", "xsi": "http://www.w3.org/2001/XMLSchema-instance"}

root = etree.Element("configuration", nsmap=nsmap)
root.set(XSI + "noNamespaceSchemaLocation", "../schema/variation-config.xsd")

strategy = etree.SubElement(root, "strategy", id="XXX")

conditions = etree.SubElement(strategy, "conditions")
scenario = etree.SubElement(conditions, COND + "scenario")

scenario.text = "A"

print(etree.tostring(root, pretty_print=True))

Output

<configuration xmlns:cond="http://www.aaa.com/orc/condition" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../schema/variation-config.xsd">
  <strategy id="XXX">
    <conditions>
      <cond:scenario>A</cond:scenario>
    </conditions>
  </strategy>
</configuration>