How to convert xml tags into dictionary using python?

Question

I am trying to add elements in a dictionary keeping key,value pair using python. My input is xml and expected output should be dictionary.

Input:-

<math>
    <elements>
        <function>
           <val>ADD</val>
        </function>
        <operator>
           <val>+</val>
        </operator>
        <function>
           <val>SUB</val>
        </function>
        <operator>
           <val>-</val>
        </operator>
    </elements>
</math>

I tried parsing and converting it into dictionary but no help. I am using lxml and don't want to use xmltodict.

code till now:- 

from lxml import etree
from lxml.etree import _ElementTree, _Element, XMLParser
tree = etree.parsexml('math.xml')
root = tree.getroot()
mathdict = {}

for item in root.findall('./math/elements/function/'):
    for d in root.findall('./math/elements/operator/'):
        mathdict[item.text] = d.text

It should return dictionary like below:- [ADD:+,SUB:-]

Answer 1

Assuming the order of the XML is always going to be "correct", you can use .iter and zip:

import xml.etree.ElementTree as ET


string = '''<math>
                <elements>
                    <function>
                       <val>ADD</val>
                    </function>
                    <operator>
                       <val>+</val>
                    </operator>
                    <function>
                       <val>SUB</val>
                    </function>
                    <operator>
                           <val>-</val>
                    </operator>
                </elements>
            </math>'''

root = ET.fromstring(string)

output = {}

functions, operators = root.iter('function'), root.iter('operator')

for function, operator in zip(functions, operators):
    output[function.find('val').text] = operator.find('val').text

print(output)
# {'ADD': '+', 'SUB': '-'}

The dictionary creation and loop can be condensed to a dict comprehension:

output = {function.find('val').text: operator.find('val').text
          for function, operator in zip(functions, operators)}