python code to concat/shrink gpx files

gpxshrink.py

# attempt to shrink gpx files and concat them to get on android device
# got zip file with gpx from http://www.phillowry.com/wasatchwatch.htm
# converted to kml with gpx2kml.com
# gaia gps bogged down with files...
# my tracks does ok with them
import sys
import xml.etree.ElementTree as et

def concat(fins, fout, stride):
    tree = et.ElementTree()
    tree.parse(fins[0])
    parent = tree._root.getchildren()[1].getchildren()[-1] #trkseg
    i = 0
    to_remove = []
    to_add = []
    for child in parent.getchildren():
        # I hate ns handling in etree!!!
        if child.tag.endswith('trkpt'):
            #import pdb;pdb.set_trace()
            if i % stride != 0:
                to_remove.append(child)
            i += 1
    for rem in to_remove:
        parent.remove(rem)
    for other in fins[1:]:
        t2 = et.ElementTree()
        t2.parse(other)
        p2 = t2._root.getchildren()[1].getchildren()[-1] #trkseg
        for child in p2.getchildren():
            # I hate ns handling in etree!!!
            if child.tag.endswith('trkpt'):
                #import pdb;pdb.set_trace()
                if i % stride == 0:
                    to_add.append(child)
                i += 1
    for node in to_add:
        parent.append(node)
    tree.write(fout)

def shrink(fin, fout, stride=2):
    tree = et.ElementTree()
    tree.parse(fin)
    # don't work silly ns...
    #parent = tree.find('trkseg')
    parent = tree._root.getchildren()[1].getchildren()[-1] #trkseg
    i = 0
    to_remove = []
    for child in parent.getchildren():
        # I hate ns handling in etree!!!
        if child.tag.endswith('trkpt'):
            if i % stride != 0:
                to_remove.append(child)
            i += 1
    for rem in to_remove:
        parent.remove(rem)
    tree.write(fout)




#shrink(open(sys.argv[1]), open(sys.argv[2], 'w'), stride=40)
concat([open('/tmp/w1.gpx'), open('/tmp/w2.gpx')], open('/tmp/w100-40.gpx', 'w'), stride=40)