#!/usr/bin/python
#
# edges.py
#
# Duplicates a list of directed edges to obtain an undirected graph.
#
# Copyright (c) 2006 Marco Colombo
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# See http://www.gnu.org/licenses/gpl.txt for a copy of the license.
#

import sys, string, re, fileinput

#
# main
#
def main(argv = None):

    # change argv if we are not running from the interactive prompt
    if argv is None:
        argv = sys.argv

    # check if we have the correct number of arguments
    if len(argv) != 2:
        print "Usage: edges.py <inputfile>"
        return 1

    try:
        # go through the input file
        for line in fileinput.input():

            # skip lines that are empty or begin with "#"
            if re.match("^\s*$|^#", line):
                continue

            # split the line
            fr, to, length = string.split(line)

            try:
                # print the existing arc
                print "%3d   %3d   %f" % (int(fr), int(to), float(length))

                # print the reversed arc
                print "%3d   %3d   %f" % (int(to), int(fr), float(length))

            except ValueError:
                pass

    except IOError:
        print "Could not open file '" + fileinput.filename() + "'."


if __name__ == "__main__":
    sys.exit(main())