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

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.