Reconstruct the itinerary in order

Given an bunch of airline tickets with [from, to], for example [MUC, LHR], [CDG, MUC], [SFO, SJC], [LHR, SFO]
please reconstruct the itinerary in order, 
[ CDG, MUC, LHR, SFO, SJC ]. 
Note: tickets can be represented as nodes

#!/usr/bin/env python

import sys

# Reads the given file which contains airline tickets
# and returns 2 hash,
#  * (1) with all the ticket info
#  * (2) wth the starting and ending points
def getTicketsFromFile(filename):
    lines = []

    # Read the file
    with open(filename, "r") as fp:
        lines = lines = fp.readlines()

    lines = map(lambda s: s.strip(), lines)

    tickets = {}
    points = {}
    for line in lines:
        if line !="":
            point = map(lambda s: s.strip(), line[1:-1].split(","))
            tickets[point[0]] = point[1]

            # create 2 nodes for each ticket (start, end) and
            # do this for all the tickets
            for p in point:
                try:
                    # Delete the key from the points if it exists to find the start and end
                    # points for the entire trip.
                    del points[p]
                except:
                    points[p] = ""

    # Find the starting point
    for k in points.keys():
        if k in tickets.keys():
            startPoint = k
            break
        
    return (tickets, startPoint)


if __name__ == "__main__":
    (tickets, startPoint) = getTicketsFromFile(sys.argv[1])

    # print the order
    point = startPoint
    while True:
        print point,
        
        try:
            point = tickets[point]
        except:
            break