Sample KML file (placemarks)

Handle it in code

Each snippet below was run against this exact file with Python 3.14.4 and Node 24.15.0 when this page was built, and the output shown is what it printed.

Python

GPX stores lat and lon as attributes; KML writes "lon,lat,alt" text, the opposite order. Read each in its own order and validate the ranges, or points end up swapped across the globe.

import xml.etree.ElementTree as ET

points = []  # (lat, lon)
for el in ET.parse("placemarks.kml").getroot().iter():
    tag = el.tag.rsplit("}", 1)[-1]
    if tag in ("trkpt", "rtept", "wpt"):  # GPX
        points.append((float(el.get("lat")), float(el.get("lon"))))
    elif tag == "coordinates":  # KML: lon,lat[,alt] tuples
        for t in el.text.split():
            lon, lat = map(float, t.split(",")[:2])
            points.append((lat, lon))
bad = [p for p in points if not (-90 <= p[0] <= 90 and -180 <= p[1] <= 180)]
print(f"{len(points)} points, first at lat {points[0][0]}, lon {points[0][1]}")
print(f"{len(bad)} out of range" if bad else "all within range")

Run against this file, it prints: 4 points, first at lat 51.5072, lon -0.1276 all within range