header = 'lat', 'lon', 'ele', 'time'
with open('output.csv', 'w') as f:
    writer = csv.writer(f)
writer.writerow(header)
root = lxml.etree.fromstring(x)
for trkpt in root.iter('{%s}trkpt' % NS):
    lat = trkpt.get('lat')
lon = trkpt.get('lon')
ele = trkpt.find('{%s}ele' % NS).text
time = trkpt.find('{%s}time' % NS).text
row = lat, lon, ele, time
writer.writerow(row)
XML в CSV в Python