Trip.py

"""
pyOTPA's representation of a single trip.

Currently just using a Tuple to keep storage overhead low, given there are
potentially 100K plus trips we're going to deal with.
"""

import copy
from datetime import datetime

import otp_config

#Note that trip's Origin and Dest coords are in the EPSG of otp_config
#OTP_ROUTER_EPSG
TRIP_EPSG = otp_config.OTP_ROUTER_EPSG

ORIGIN = 0              # This is a tuple in X, Y format:- trip origin.
DEST = ORIGIN+1         # This is a tuple in X, Y format:- trip destination.
START_DTIME = DEST+1    # A python datetime object
O_ZONE = START_DTIME+1  # A string representing a zone, origin
D_ZONE = O_ZONE+1       # A string representing a zone, destination
ID = D_ZONE+1           # A trip ID (string)

def new_trip(origin_geom, dest_geom, start_date_time, origin_zone,
        dest_zone, trip_id):
    trip = (origin_geom, dest_geom, start_date_time, origin_zone, \
        dest_zone, trip_id)
    return trip

def new_trip_with_updated_start(exist_trip, new_start_dt):
    upd_time_trip = new_trip(
        exist_trip[ORIGIN],
        exist_trip[DEST],
        new_start_dt,
        exist_trip[O_ZONE],
        exist_trip[D_ZONE],
        exist_trip[ID])
    return upd_time_trip

def get_trips_srs():
    from osgeo import osr
    trips_srs = osr.SpatialReference()
    trips_srs.ImportFromEPSG(TRIP_EPSG)
    return trips_srs

def print_trip(trip):
    print "trip '%s': %f,%f to %f,%f at %s ('%s'->'%s')" \
        % (str(trip[ID]), trip[ORIGIN][0], trip[ORIGIN][1],
           trip[DEST][0], trip[DEST][1], 
           trip[START_DTIME], trip[O_ZONE], trip[D_ZONE])
    return

################
# Useful Ops on a list of trips.

def get_trip_req_start_dts(trips_by_id, trip_req_start_date):
    """This function is a result of earlier storing only a time for each trip,
    not a datetime."""
    trip_req_start_dts = {}
    for trip_id, trip in trips_by_id.iteritems():
        if isinstance(trip[START_DTIME], datetime):
            trip_req_start_dts[trip_id] = trip[START_DTIME]
        else:
            trip_req_start_dts[trip_id] = datetime.combine(trip_req_start_date,
                trip[START_DTIME])
    return trip_req_start_dts

def get_trips_subset_by_ids(trip_results_dict, trip_ids_to_select):
    trip_results_filtered = {}
    for trip_id in trip_ids_to_select:
        try:
            trip_results_filtered[trip_id] = trip_results_dict[trip_id]
        except KeyError:
            raise ValueError("Input trip_results_dict didn't contain at "\
                "least one of the trip IDs ('%s') you requested in "\
                "trip_ids_to_select." % trip_id)
    return trip_results_filtered

def get_trips_subset_by_ids_to_exclude(trip_results_dict, trip_ids_to_exclude):
    # In the excluding IDs case:- start by creating a copy of the entire 
    # first dict:- since it will be faster to just delete dictionary entries
    # that are excluded. copy.copy just creates a new dictionary pointing to
    # the same actual entries in memory, so this won't waste lots of space.
    trip_results_filtered = copy.copy(trip_results_dict)
    for trip_id in trip_ids_to_exclude:
        try:
            del(trip_results_filtered[trip_id])
        except KeyError:
            print "Warning: Input trip_results_dict didn't contain at "\
                "least one of the trip IDs ('%s') you requested to exclude "\
                "in trip_ids_to_exclude." % trip_id
    return trip_results_filtered