Merge several gpx files into one

merge.py

import gpxpy.parser as parser
import gpxpy.gpx as gpx
import os
import math
import datetime

## functions
def min_max_timestamp(parsed):
    min_ts = parsed.tracks[0].segments[0].points[0].time
    max_ts = parsed.tracks[0].segments[0].points[0].time
    for track in parsed.tracks:
        for segment in track.segments:
            for point in segment.points:
                if point.time < min_ts:
                    min_ts = point.time
                if point.time > max_ts:
                    max_ts = point.time
    #print("Min, max for ", parsed, "is: ")
    #print(min_ts, max_ts)
    return (min_ts, max_ts)

def flat_points(parsed):
    points = []
    for track in parsed.tracks:
        for segment in track.segments:
            points += segment.points
    return points

## end functions


files = [f for f in os.listdir('.') if os.path.isfile(f)]
print(files)
output = 'output.gpx'
if output in files:
  files.remove(output)
files.remove(__file__)


# Get min and max timestamps
min_timestamp = None
max_timestamp = None
errors = []
# f.tracks[0].segments[0].points[0]
all_points = []
all_min_max_timestamps = []
for file in files:
    try:
        p = parser.GPXParser(open(file, 'r')).parse()
        all_min_max_timestamps.extend(min_max_timestamp(p))
        all_points += flat_points(p)
        #file.close()
    except Exception as e:
        print("Could not parse file " , file)
        print("Error: ", e)
        errors.append(file)

print("\nAll the files that could not be loaded: ")
print(errors)
print(len(all_points))
print("Min and max times")
all_min_max_timestamps.sort()
min_timestamp = all_min_max_timestamps[0]
max_timestamp = all_min_max_timestamps[-1]
print(min_timestamp, max_timestamp)


duration = 5 * 60* 60 # 5 hours
interval = math.floor(duration / len(all_points))
if interval < 1:
    interval = 1

print("Interval between each point is ", interval)
all_points.sort(key = lambda point: point.time)

# overwritting this so the activity gets the current date
min_timestamp = datetime.datetime.now() - datetime.timedelta(seconds=duration)

for index, point in enumerate(all_points):
    point.time = min_timestamp + datetime.timedelta(seconds=(index * interval))

# create new gpx file
new_file = gpx.GPX()
track = gpx.GPXTrack()
segment = gpx.GPXTrackSegment()

track.segments.append(segment)
new_file.tracks.append(track)

segment.points.extend(all_points)

with open(output, 'a') as f:
    f.write(new_file.to_xml())