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I'm trying to use lxml.etree to reproduce the CDA example found in the CDA QuickStart Guide found here.

In particular, I'm running into issues with namespaces trying to recreate this element.

<ClinicalDocument xmlns="urn:hl7-org:v3" xmlns:mif="urn:hl7-org:v3/mif" 
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
xsi:schemaLocation="urn:hl7-org:v3 CDA.xsd">

The code I'm using is as follows

root = etree.Element('ClinicalDocument',
                    nsmap={None: 'urn:hl7-org:v3',
                           'mif': 'urn:hl7-org:v3/mif',
                           'xsi': 'http://www.w3.org/2001/XMLSchema-instance',
                           '{http://www.w3.org/2001/XMLSchema-instance}schemaLocation': 'urn:hl7-org:v3 CDA.xsd'})

The problem is with the schemaLocation entry in nsmap. lxml appears to be trying to validate the value and gives the error 

ValueError: Invalid namespace URI u'urn:hl7-org:v3 CDA.xsd'

Am I specifying the schemaLocation value incorrectly? Is there a way to force lxml to accept any string value? Or is the value in the example simply intended to be a placeholder that I am supposed to replace with something else?

user3419537
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1 Answers1

16

nsmap is a mapping of prefixes to namespace URIs. urn:hl7-org:v3 CDA.xsd is a valid value for the xsi:schemaLocationattribute, but it is not a valid namespace URI.

The solution to a similar question, How to include the namespaces into a xml file using lxmf?, works here too. Use QName to create the xsi:schemaLocation attribute.

from lxml import etree

attr_qname = etree.QName("http://www.w3.org/2001/XMLSchema-instance", "schemaLocation")

root = etree.Element('ClinicalDocument',
                     {attr_qname: 'urn:hl7-org:v3 CDA.xsd'},
                     nsmap={None: 'urn:hl7-org:v3',
                            'mif': 'urn:hl7-org:v3/mif',
                            'xsi': 'http://www.w3.org/2001/XMLSchema-instance',
                            })
mzjn
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