XML Element Tree - appending to existing elements and attributes with ET.SubElement()? - python-3.x

Question

I have the following function which builds up a re-usable XML SOAP envelope:
def get_xml_soap_envelope():
"""
Returns a generically re-usable SOAP envelope in the following format:
<soapenv:Envelope>
<soapenv:Header/>
<soapenv:Body />
</soapenv:Envelope>
"""
soapenvEnvelope = ET.Element('soapenv:Envelope')
soapenvHeader = ET.SubElement(soapenvEnvelope, 'soapenv:Header')
soapenvBody = ET.SubElement(soapenvEnvelope, 'soapenv:Body')
return soapenvEnvelope
Fairly simple stuff so far.
I was wondering now, would it be possible to append attributes (such as xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance") to the soapenv:Envelope element?
And if I also wanted to append the following XML:
<urn:{AAction} soapenv:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/">
<AUserName>{AUserName}</AUserName>
<APassword>{APassword}</APassword>
</urn:{AAction}>
To the soapenv:Body such that I would have something like this:
if __name__ == "__main__":
soapenvEnvelope = get_xml_soap_envelope()
actions = {
'AAction': 'UserLogin',
}
soapAAction = ET.Element('urn:{AAction}'.format(**actions))
soapenvEnvelope.AppendElement(soapAAction, 'soapenv:Body')
So, I could specify a target node and the Element to append to?

Answer 1

Let's start from the bad news: Your function to create the SOAP envelope
(get_xml_soap_envelope) is wrong as it fails to specify at least
xmlns:soapenv="...".
Actually all other namespaces to be used should be also specified here.
A proper function creating the SOAP envelope should be somenting like this:
def get_xml_soap_env():
"""
Returns a generically re-usable SOAP envelope in the following format:
<soapenv:Envelope xmlns:soapenv="...", ...>
<soapenv:Header/>
<soapenv:Body />
</soapenv:Envelope>
"""
ns = {'xmlns:soapenv': 'http://schemas.xmlsoap.org/soap/envelope/',
'xmlns:xsi': 'http://www.w3.org/2001/XMLSchema-instance',
'xmlns:urn': 'http://dummy.urn'}
env = ET.Element('soapenv:Envelope', ns)
ET.SubElement(env, 'soapenv:Header')
ET.SubElement(env, 'soapenv:Body')
return env
Note that ns dictionary contains also other namespaces, which will be
needed later, a.o. xsi namespace.
A possible alternative is to define ns outside of this function and pass it as
a parameter (your choice).
When I ran:
env = get_xml_soap_env()
print(ET.tostring(env, encoding='unicode', short_empty_elements=True))
the printout (reformatted by me for readability) was:
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"
xmlns:urn="http://dummy.urn"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<soapenv:Header />
<soapenv:Body />
</soapenv:Envelope>
Note that this time proper namespaces are included.
Then, to add the Action element and its children, define the following function:
def addAction(env, action, subelems):
body = env.find('soapenv:Body')
actn = ET.SubElement(body, f'soapenv:{action}')
for k, v in subelems.items():
child = ET.SubElement(actn, k)
child.text = v
When I ran:
subelems = {'AUserName': 'Mark', 'APassword': 'Secret!'}
addAction(env, 'UserLogin', subelems)
and printed the whole XML tree again, the result was:
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"
xmlns:urn="http://dummy.urn" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<soapenv:Header />
<soapenv:Body>
<soapenv:UserLogin>
<AUserName>Mark</AUserName>
<APassword>Secret!</APassword>
</soapenv:UserLogin>
</soapenv:Body>
</soapenv:Envelope>