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Json – To print the data after replacing the given expression with the values in XML file using "ElementTree" library

NaviB
February 19, 2024
213 views
0 votes
2 Answers

Given XML file snippet is:

<?xml version="1.0" standalone="yes"?>
<event_configuration family="21" version="2">
    <pqr subtype="abc">
    <event val="73002" name="$MyCpu"> </event>
    <event val="73003" name="$MyCpuKernel"> </event>

    <metric name="Ratio" expression="$MyCpuKernel / $MyCpu"> </metric>
    </pqr>
</event_configuration>

I have parsed this xml file using "ElementTree" library in Python, please find the code below:

    def parse_xml_to_json(self):
        data = {'metric': []}
        root = ET.fromstring(self.xml_file)

        for element in root.findall('.//*'):
            element_type = element.tag
            if element_type not in ["pqr", "stu", "vwx"]:
                continue
            subtype_name = element.attrib['subtype']
            event_map = {}
            for event in element.findall('.//event'):
                event_name = event.attrib['name']
                val_value = event.attrib['val']
                event_map[event_name] = val_value

            for metric in element.findall('metric'):
                expression = metric.attrib['expression']
                metric_name = metric.attrib['name']
          
                for event_name, val_value in event_map.items():
                    expression = expression.replace(event_name, val_value)

                data['metric'].append({
                    'Name': metric_name,
                    'Expression': expression,
                    'Type': element_type
                })

        return data

I am getting the output, but this code is unable to replace the event name present inside "Expression" with the val_value as shown below:-

Output:

{
"metric": [
    {
        "Name": "Ratio",
        "Expression": "73002Kernel / 73002",
        "Type": "pqr"
    },
    ....
    ....
]
}

Here, we can see in the "Expression" it should print "73003 / 73002".
I am unable to think of how to solve this issue. Is it possible to use regex here, how to apply it? Please suggest.

Answers

You can change the XML and create than your JSON. The XML attribute values can be .get() and .set() For the expression attribute you can use an f-string with the values:

Suggested solution in your code:

import xml.etree.ElementTree as ET

class Whatever:
    def __init__(self):
        self.xml_file = "eventConfig.xml"
    
    def parse_xml_to_json(self):
        data = {'metric': []}
        root = ET.parse(self.xml_file) # cahnged parse from file not from string

        for element in root.findall('.//*'):
            element_type = element.tag
            if element_type not in ["pqr", "stu", "vwx"]:
                continue
            subtype_name = element.attrib['subtype']
            event_map = {}
            
            for metric in element.findall('metric'):
                expression = metric.attrib['expression']
                metric_name = metric.attrib['name']

            mycpu = root.find(".//event[@name = '$MyCpu']").get('val')
            mycpukernel = root.find(".//event[@name = '$MyCpuKernel']").get('val')
            tex = f"{mycpu}/{mycpukernel}"
            #metric = root.find(".//metric[@expression]").set('expression', tex)

            data['metric'].append({
                'Name': metric_name,
                'Expression': tex,
                'Type': element_type
            })

        return data
    
if __name__ == "__main__":
    p = Whatever()
    res = p.parse_xml_to_json()
    print(res)

Output:

{'metric': [{'Name': 'Ratio', 'Expression': '73002/73003', 'Type': 'pqr'}]}

Here is an example how you can use re.sub to replace the values in expression:

import re
import xml.etree.ElementTree as ET


def parse_xml_to_json(xml_file):
    data = {"metric": []}
    root = ET.fromstring(xml_file)

    for element in root.findall(".//*"):
        element_type = element.tag
        if element_type not in ["pqr", "stu", "vwx"]:
            continue
        subtype_name = element.attrib["subtype"]
        event_map = {}
        for event in element.findall(".//event"):
            event_name = event.attrib["name"]
            val_value = event.attrib["val"]
            event_map[event_name] = val_value

        for metric in element.findall("metric"):
            expression = metric.attrib["expression"]
            metric_name = metric.attrib["name"]

            for event_name, val_value in event_map.items():
                expression = re.sub(
                    rf"{re.escape(event_name)}b", val_value, expression
                )

            data["metric"].append(
                {"Name": metric_name, "Expression": expression, "Type": element_type}
            )

    return data


xml_file = """
<?xml version="1.0" standalone="yes"?>
<event_configuration family="21" version="2">
    <pqr subtype="abc">
    <event val="73002" name="$MyCpu"> </event>
    <event val="73003" name="$MyCpuKernel"> </event>

    <metric name="Ratio" expression="$MyCpuKernel / $MyCpu"> </metric>
    </pqr>
</event_configuration>"""

print(parse_xml_to_json(xml_file))

Prints:

{'metric': [{'Name': 'Ratio', 'Expression': '73003 / 73002', 'Type': 'pqr'}]}

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