An example to get the root of mxGraphModel from draw io file.

get_graph_model.py

#!python
# coding: utf-8

import sys
import zlib
import base64
import xml.etree.ElementTree as ET
from urllib.parse import unquote

def decode_drawio(filename):
    tree = ET.parse(filename)
    root = tree.getroot()
    is_compressed = root.attrib.get('compressed', None) == 'true'
    if is_compressed:
        raw = tree.find('diagram')
        data = base64.b64decode(raw.text)
        zobj = zlib.decompressobj(wbits=-15)
        xml = zobj.decompress(data).decode('utf-8')
        xml = unquote(xml)
        xml = ET.ElementTree(ET.fromstring(xml))
        xml = xml.getroot()
    else:
        raw = tree.find('diagram/mxGraphModel')
        xml = raw

    return xml

if __name__ == '__main__':
    xml = decode_drawio(sys.argv[1])
    print(xml)