python lxml attribute namespaces within namespaces

Question

In the documentation I'm looking at for a file upload, it needs this specific tag at the beginning of the xml file:

<oclcPersonas xmlns="http://worldcat.org/xmlschemas/IDMPersonas-2.2" 
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
xsi:schemaLocation="http://worldcat.org/xmlschemas/IDMPersonas-2.2 IDMPersonas-2.2.xsd">

I'm trying to use the lxml.etree library to figure this out.

Many of the examples I've seen have a initial level of namespace for attributes that would cover the xmlns:xsi portion using this:

namespace_map = {
        None: persona_namespace,
        'xsi': "http://www.w3.org/2001/XMLSchema-instance"}

but 2 questions arise from the second portion xsi:schemaLocation

1) How would I accomplish a secondary level of namespace using lxml?

2) How do I allow the namespaces to contain a space without receiving an error (http://worldcat.org/xmlschemas/IDMPersonas-2.2 IDMPersonas-2.2.xsd)

Laurent LAPORTE · Accepted Answer · 2018-10-18 21:28:51Z

1

In your sample XML, you have :

a root element oclcPersonas in the default namespace,
a default namespace: "http://worldcat.org/xmlschemas/IDMPersonas-2.2",
a “xsi” namespace: "http://www.w3.org/2001/XMLSchema-instance",
a “schemaLocation” attribute in the “xsi” namespace.

To build this element with lxml, you need to use the fully-qualified name using curly braces (James Clark notation).

First define a dictionary which store your namespace mapping:

# your namespaces
p_url = "http://worldcat.org/xmlschemas/IDMPersonas-2.2"
xsi_url = "http://www.w3.org/2001/XMLSchema-instance"
NS = {None: p_url, 'xsi': xsi_url}

In order to build fully-qualified namespace, you can define prefixes:

# tag prefixes
P = '{' + p_url + '}'
XSI = '{' + xsi_url + '}'

Then you can define the tag names and attributes:

# tag names and attributes
root_tag = P + 'oclcPersonas'
attrs = {
    XSI + 'schemaLocation':
    "http://worldcat.org/xmlschemas/IDMPersonas-2.2 IDMPersonas-2.2.xsd"
}

The root element can be created like below:

# element
root = etree.Element(root_tag, attrib=attrs, nsmap=NS)

You should have your element:

print(etree.tounicode(root))

To answer your question:

2) How do I allow the namespaces to contain a space without receiving an error (http://worldcat.org/xmlschemas/IDMPersonas-2.2 IDMPersonas-2.2.xsd)

This is not a namespace, this is the value of the schemaLocation attribute. A simple string.

answered Oct 18, 2018 at 21:28

Laurent LAPORTE

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1 Comment

Avir94 Over a year ago

Thank you so much! Worked Perfectly

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