Useful for filling D/T Grid. Takes a finds.gpx, and a caches.gpx and spits out a caches.gpx containing only caches needed to get D/T grid

Filter DT Grid.py

#! /usr/bin/env python3.4

import xml.etree.cElementTree as ET

namespaces = {
    'xmlns': 'http://www.topografix.com/GPX/1/0',
    'groundspeak': 'http://www.groundspeak.com/cache/1/0/1'
}

def d_t_grid(gpx):
    '''Accepts a gps file path, then creates an array of arrays and populate it with
    number of caches for each difficulty and terrain rating. Difficulty is the first
    index, terrain is the second.

    Ratings are doubled to make them integers so they can be used for array index
    (probably should use dicts instead)
    '''
    grid = [[0 for x in range(9)] for x in range (9)]
    tree = ET.parse(gpx)
    for wpt in tree.iterfind('xmlns:wpt', namespaces=namespaces):
        difficulty = wpt.find('groundspeak:cache/groundspeak:difficulty', namespaces=namespaces).text
        terrain = wpt.find('groundspeak:cache/groundspeak:terrain', namespaces=namespaces).text
        d_int = int(float(difficulty)*2) - 2
        t_int = int(float(terrain)*2) - 2
        grid[d_int][t_int] += 1
    return grid

def filter_by_grid(gpx, grid, output):
    ET.register_namespace('', 'http://www.topografix.com/GPX/1/0')
    ET.register_namespace('groundspeak', 'http://www.groundspeak.com/cache/1/0/1')
    tree = ET.parse(gpx)
    for wpt in tree.findall('xmlns:wpt', namespaces=namespaces):
        difficulty = wpt.find('groundspeak:cache/groundspeak:difficulty', namespaces=namespaces).text
        terrain = wpt.find('groundspeak:cache/groundspeak:terrain', namespaces=namespaces).text
        d_int = int(float(difficulty)*2) - 2
        t_int = int(float(terrain)*2) - 2
        if grid[d_int][t_int] != 0:
            tree.getroot().remove(wpt)
        else:
            #Add namespace attribute to groundspeak:cache because otherwise L4C doesn't get the name properly
            cache = wpt.find('groundspeak:cache', namespaces=namespaces)
            cache.set('xmlns:groundspeak', 'http://www.groundspeak.com/cache/1/0/1')

    tree.write(output, encoding='UTF-8', xml_declaration=True)

def main():
    import argparse
    parser = argparse.ArgumentParser(description='Filter Geocaches by D/T Grid')
    parser.add_argument('finds', help='a gpx file containing all finds')
    parser.add_argument('caches', help='a gpx file containing unfound caches')
    parser.add_argument('output', help='filename to use for new GPX file')
    args = parser.parse_args()
    filter_by_grid(args.caches, d_t_grid(args.finds), args.output)

if __name__ == '__main__':
    main()