I'm trying to update the attribute value in the xml using Python ElementTree, when I try to access the attribute then I'm getting a message

None

Here is the xml data

xmldata='''<?xml version="1.0" encoding="UTF-8"?>
<WMS_Capabilities version="1.3.0" xmlns="http://www.opengis.net/wms" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.opengis.net/wms http://schemas.opengis.net/wms/1.3.0/capabilities_1_3_0.xsd">
    <!-- Service Metadata -->
    <Capability>
        <Request>
            <GetCapabilities>
                <Format>text/xml</Format>
                <DCPType>
                    <HTTP>
                        <Get>
                            <OnlineResource xmlns:xlink="http://www.w3.org/1999/xlink"
                            xlink:type="simple"
                            xlink:href="http://localhost:8080" />
                        </Get>
                        <Post>
                            <OnlineResource xmlns:xlink="http://www.w3.org/1999/xlink"
                            xlink:type="simple"
                            xlink:href="http://localhost:8080" />
                        </Post>
                    </HTTP>
                </DCPType>
            </GetCapabilities>
            <GetMap>
                <Format>image/jpg</Format>
                <Format>image/png</Format>
                <DCPType>
                    <HTTP>
                        <Get>
                            <OnlineResource xmlns:xlink="http://www.w3.org/1999/xlink" 
                            xlink:type="simple" 
                            xlink:href="http://localhost:8080" />
                        </Get>
                    </HTTP>
                </DCPType>
            </GetMap>
            <GetFeatureInfo>
                <Format>text/xml</Format>
                <Format>text/plain</Format>
                <Format>text/html</Format>
            </GetFeatureInfo>
        </Request>
        <Exception>
            <Format>XML</Format>
            <Format>INIMAGE</Format>
            <Format>BLANK</Format>
        </Exception>
    </Capability>
</WMS_Capabilities>'''

ns='{http://www.opengis.net/wms}'
myroot = ET.fromstring(xmldata)
for x in myroot.findall(ns "Capability/"   ns   "Request/"   ns   "GetMap/"   ns   "DCPType/"   ns   "HTTP/"   ns   "Get/"   ns   "OnlineResource"):
    print(x)

output:

<Element '{http://www.opengis.net/wms}OnlineResource' at 0x7f0e0ab8e130>

selectedNode=myroot.find(ns   "Capability/"   ns   "Request/"   ns   "GetMap/"   ns   "DCPType/"   ns   "HTTP/"   ns   "Get/"   ns   "OnlineResource").tag
print(selectedNode)

output:

{http://www.opengis.net/wms}OnlineResource

selectedAttribute=myroot.find(ns   "Capability/"   ns   "Request/"   ns   "GetMap/"   ns   "DCPType/"   ns   "HTTP/"   ns   "Get/"   ns   "OnlineResource").attrib['xlink:href']
print(selectedAttribute)

output:

 Traceback (most recent call last): File "<string>", line 59, in
 <module> KeyError: 'xlink:href'

Here I wanted to update the value of the attribute 'xlink:href' and save the xml file.

I'm not able to access the attribute, and getting an error while trying to access it. I'm not getting whether I have followed the right method to access attribute value or not. Need suggestions to update the value.

I have referred below mentioned links,

1. How to extract xml attribute using Python ElementTree
2. How can I get the href attribute of *any* element in an XML (included deeply nested ones) using xpath?
3. How do I extract value of XML attribute in Python?
4. Reading XML file and fetching its attributes value in Python
5. https://docs.python.org/3/library/xml.etree.elementtree.html
6. https://www.edureka.co/blog/python-xml-parser-tutorial/

CodePudding user response：

It seems that in order to access the href attribute, the field name must be prefixed with the value of the xlink attribute. Continuing from your sample code:

>>> node = myroot.find(ns   "Capability/"   ns   "Request/"   ns   "GetMap/"   ns   "DCPType/"   ns   "HTTP/"   ns   "Get/"   ns   "OnlineResource")
>>> node.attrib['{http://www.w3.org/1999/xlink}href']
'http://localhost:8080'

If you don't know this prefix beforehand, you should still be able to find the href field at runtime with this method:

for key, val in node.attrib.items():
    if key.endswith('href'):
        print(val)