Unable to append the gml string to xml using lxml in python

Question

test_gml.py

from lxml import etree
import lxml
xml_response = lxml.etree.Element('xmlResponse')
mapping = lxml.etree.SubElement(xml_response,'mapping',{"id":"AHGJHKSHQWEIUELQWDKJQEDH"})
services_element = lxml.etree.SubElement(mapping, 'service_name')
services_element.text = "gml_info"
gml_info = '''<gml:Envelope srsName="EPSG:4326">
        <gml:lowerCorner>1 2</gml:lowerCorner>
        <gml:upperCorner>10 20</gml:upperCorner>
    </gml:Envelope>'''
services_element = lxml.etree.SubElement(mapping, 'gml_info')
services_element.text = gml_info
print (etree.tostring(xml_response))

When I try to run the above code I am getting the below response where gml tags are not preserved.

Response:

b'<xmlResponse><mapping id="AHGJHKSHQWEIUELQWDKJQEDH">
<service_name>gml_info</service_name>
<gml_info>&lt;gml:Envelope 
srsName="EPSG:4326"&gt;\n\t\t&lt;gml:lowerCorner&gt;1 
2&lt;/gml:lowerCorner&gt;\n\t\t&lt;gml:upperCorner&gt;10 
20&lt;/gml:upperCorner&gt;\n\t&lt;/gml:Envelope&gt;</gml_info>
</mapping></xmlResponse>'

Answer 1

You have to add it as xml subtree and not as text node.

from lxml import etree
import lxml
import io

xml_response = lxml.etree.Element('xmlResponse')
mapping = lxml.etree.SubElement(xml_response, 'mapping', {"id": "AHGJHKSHQWEIUELQWDKJQEDH"})
services_element = lxml.etree.SubElement(mapping, 'service_name')
services_element.text = "gml_info"

gml = io.StringIO('''<root xmlns:gml="gml"><gml:Envelope srsName="EPSG:4326">\
<gml:lowerCorner>1 2</gml:lowerCorner>\
<gml:upperCorner>10 20</gml:upperCorner>\
</gml:Envelope></root>''')
gml_info = etree.parse(gml).getroot()


services_element = lxml.etree.SubElement(mapping, 'gml_info')
services_element.extend(gml_info)

print(etree.tostring(xml_response))

I had to add <root xmlns:gml="gml"> element with namespace declaration for gml (you should change it for a real link). Without it you will get error:

lxml.etree.XMLSyntaxError: Namespace prefix gml on Envelope is not defined, line 1, column 41