kml2gpx.py

#!/usr/bin/python
# https://timwise.co.uk/2014/02/03/converting-kml-to-gpx-with-python/
# https://gist.github.com/timabell/8791116

import argparse
import xml.sax

parser = argparse.ArgumentParser(description='Convert annoying google android my tracks kml data to sensible gpx files')
parser.add_argument('input_file')

args = parser.parse_args()
input = args.input_file

class KmlParser(xml.sax.ContentHandler):
	def __init__(self):
		self.in_tag=0
		self.chars=""
		self.when=""
		self.started=0
	def startElement(self, name, attrs):
		if name == "gx:coord":
			self.in_tag=1
			self.chars=""
		if name == "when":
			self.in_tag=1
			self.chars=""
		if name == "gx:Track":
			if self.started:
				print '</trkseg>'
				print '<trkseg>'
	def characters(self, char):
		if self.in_tag:
			self.chars += char
	def endElement(self, name):
		if name == "when":
			self.in_coord=0
			self.when = self.chars
			self.chars=""
		if name == "gx:coord":
			self.in_coord=0
			self.started=1
			coords=self.chars
			self.chars=""
			coords = coords.split()
			print '\t<trkpt lat="%s" lon="%s">' % (coords[1],coords[0])
			if len(coords)>2:
				print '\t\t<ele>%s</ele>' % coords[2]
			print '\t\t<time>%s</time>' % self.when
			print "\t</trkpt>"

print """<?xml version="1.0" encoding="UTF-8"?>
<gpx version="1.0"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	creator="tim-abell kml to gpx converter - https://gist.github.com/timabell/8791116"
	xmlns="http://www.topografix.com/GPX/1/0"
	xsi:schemaLocation="http://www.topografix.com/GPX/1/0 http://www.topografix.com/GPX/1/0/gpx.xsd">
<trk><trkseg>"""

parser = xml.sax.make_parser()
parser.setContentHandler(KmlParser())
parser.parse(open(input,"r"))

print """</trkseg></trk>
</gpx>
"""

Are there multiple kml versions? This file looks very different.
https://www.lamarathon.com/assets/kml/2018-LA-Marathon-Route.kml
It's no biggy to parse it though.