Custom string represention

import collections
import re
import sys

class Command:
    """
    A Command is an object consisting of a start_floor
    and a list of Transition instances
    """

    def __init__(self, start_floor, transitions):
        self.start_floor = start_floor
        self.transitions = transitions

    def __str__(self):
        return "Command, \n\tstart_floor = {0}\n\ttransitions = {1}".format(
            self.start_floor, self.transitions)

class Transition:
    """
    A transition is an object consisting of an origin floor
    and destination floor
    """

    def __init__(self, origin, destination):
        self.origin = origin
        self.destination = destination

    def __str__(self):
        return "Transition {0} -> {1}".format(self.origin, self.destination)


def parse_command_string(s):
    """
    Given a COMMAND_STRING, return a 2-tuple of START_FLOOR and
    list of ORIGINS_AND_DESTINATIONS, where ORIGINS_AND_DESTINATIONS
    is a namedtuple of origin and destination.
    """
    start_floor, origins_and_destinations = s.split(':')
    start_floor = int(start_floor)

    command = Command(start_floor, [])

    for o_d in origins_and_destinations.split(','):
        o,d = [ int(i) for i in o_d.split('-') ]
        print start_floor, o,d
        command.transitions.append(Transition(o,d))

    return command


def commands(filename):
    """
    Given a FILENAME, open the file and return each line as a command.
    """
    f = file(filename).read()

    for command_string in f.split('\n'):
        print command_string
        yield parse_command_string(command_string)


def main(document_name):
    """
    Given a FILENAME return a concordance of it's data.
    """
    for i, command in enumerate(commands(document_name)):
        print command


if __name__ == '__main__':
    input_file='input.dat'
    main(input_file)