How can I change the namespace of an attribute in xml with python?

Question

In my case i have the following code:

from lxml import etree as et
from lxml.builder import ElementMaker

WSS_SCHEMA = "http://schemas.xmlsoap.org/ws/2002/12/secext"
ACTOR_SCHEMA = "http://xpto"
VERSION_SCHEMA = "2"

NSMAP = {
    'wss': WSS_SCHEMA,
    'S': ACTOR_SCHEMA,
    'at': VERSION_SCHEMA,
}

WSS = ElementMaker(namespace=WSS_SCHEMA, nsmap=NSMAP)

security = WSS.Security()

security.set("{%s}actor" % ACTOR_SCHEMA, ACTOR_SCHEMA)
security.set("{%s}Version" % VERSION_SCHEMA, VERSION_SCHEMA)

print(et.tostring(security, encoding="unicode"))

And I am getting this in the output:

<wss:Security xmlns:wss="http://schemas.xmlsoap.org/ws/2002/12/secext" xmlns:S="http://xpto" xmlns:at="2" S:actor="http://xpto" at:Version="2"/>

My desired output is this:

<wss:Security xmlns:wss="http://schemas.xmlsoap.org/ws/2002/12/secext" S:actor="http://xpto" at:Version="2"/>

Does anyone have any suggestions on how I can remove these two attributes, or how I can add only the desired attributes with their respective namespaces?

Answer 1

Namespaces must be defined somewhere in the doc before using them.

from lxml import etree as et
from lxml.builder import ElementMaker

WSS_SCHEMA = "http://schemas.xmlsoap.org/ws/2002/12/secext"
ACTOR_SCHEMA = "http://xpto"
VERSION_SCHEMA = "example.com"

RNSMAP = {
    'S': ACTOR_SCHEMA,
    'at': VERSION_SCHEMA,
}

NSMAP = {
    'wss': WSS_SCHEMA
}


WSS = ElementMaker(namespace=WSS_SCHEMA, nsmap=NSMAP)

security = WSS.Security()

security.set("{%s}actor" % ACTOR_SCHEMA, ACTOR_SCHEMA)
security.set("{%s}Version" % VERSION_SCHEMA, "2")

wrapper = ElementMaker(namespace=ACTOR_SCHEMA, nsmap=RNSMAP)

root = wrapper.Wrapper(security)

print(et.tostring(root, encoding="unicode"))

Result

<S:Wrapper xmlns:S="http://xpto" xmlns:at="example.com">
    <wss:Security xmlns:wss="http://schemas.xmlsoap.org/ws/2002/12/secext" 
        S:actor="http://xpto" at:Version="2"/>
</S:Wrapper>

If a single element is required then all namespaces must be defined there

WSS_SCHEMA = "http://schemas.xmlsoap.org/ws/2002/12/secext"
ACTOR_SCHEMA = "http://xpto"
VERSION_SCHEMA = "example.com"
NSMAP = {
    'wss': WSS_SCHEMA,
    'S': ACTOR_SCHEMA,
    'at': VERSION_SCHEMA,
}
WSS = ElementMaker(namespace=WSS_SCHEMA, nsmap=NSMAP)

security = WSS.Security()

security.set("{%s}actor" % ACTOR_SCHEMA, ACTOR_SCHEMA)
security.set("{%s}Version" % VERSION_SCHEMA, "2")

print(et.tostring(security, encoding="unicode"))

Result (manually indented)

<wss:Security 
     xmlns:S="http://xpto"
     xmlns:at="example.com" 
     xmlns:wss="http://schemas.xmlsoap.org/ws/2002/12/secext"
     S:actor="http://xpto"
     at:Version="2"/>