def save(self):
# create gpx document from existing gpx file
today = datetime.date.today().strftime("%Y-%m-%d")
gpx_file = os.path.join(self.directory, today + '.xml')
document = Document(children=[], name=today)
if os.path.exists(gpx_file):
document = document.readGPX(gpx_file)
# add track to document
segment = TrackSegment(points=self.track_points)
document.append(Track(segments=[segment]))
# add way points to document
for wp in self.way_points:
document.append(wp)
# write or overwrite gpx file
f = open(gpx_file, "wb")
f.write(document.toGPX().toprettyxml(encoding="utf-8"))
f.close()
self.track_points = []
self.way_points = []
