Olympic Ticket Inferer

olympics.py

#!/usr/bin/env python
#
# Find prices of all possibilities of ticket allocations in the London
# 2012 Olympic lottery.
#
from itertools import chain, combinations
import re
import fileinput

def remove_pound(s):
    "Strip the pound sign from a cost."
    match = re.search('\d+\.\d{2}', s)
    return float(match.group(0))

class Session:
    def __init__(self):
        self.sport = ''
        self.code = ''
        self.datetime = ''
        self.venue = ''
        self.price_category = ''
        self.quantity = ''
        self.total_cost = ''
        self.maximum_cost = ''
   
    @property
    def cost(self):
        return remove_pound(self.total_cost)

    @property
    def max_cost(self):
        return remove_pound(self.maximum_cost)
       
    def __str__(self):
        return "%s (%s)" % (self.sport, self.code)
   
def powerset(iterable):
    "powerset([1,2,3]) --> () (1,) (2,) (3,) (1,2) (1,3) (2,3) (1,2,3)"
    s = list(iterable)
    return chain.from_iterable(combinations(s, r) for r in range(len(s)+1))
   
Postage_Cost = 6
   
def calculate_prices(options, overhead = Postage_Cost):
    prices = {}
    for tickets in powerset(options):
        single_price = [t for t in tickets if t.max_cost == t.cost]
        dual_price = [t for t in tickets if t not in single_price]
        assert len(single_price) + len(dual_price) == len(tickets)
        for high_priced in powerset(dual_price):
            rest = [t for t in tickets if t not in high_priced]
            cost = sum(session.max_cost for session in high_priced)
            cost += sum(session.cost for session in rest)
            if cost > 0:
                cost += overhead
            seats = list(chain([str(s) + '*' for s in high_priced],
                               [str(s) for s in rest]))
            prices.setdefault(cost, []).append(seats)
    return prices

Fields = { 'Session code' : 'code',
           'Date/time' : 'datetime',
           'Venue' : 'venue',
           'Price Category' : 'price_category',
           'Quantity' : 'quantity',
           'Total cost' : 'total_cost',
           'Total maximum cost' : 'maximum_cost' }

def parse_email(line_iter):
    sessions = []
    current = None
    for line in line_iter:
        sport = re.match("\s+Sport: (.+)", line)
        if sport:
            if current:
                sessions.append(current)
            current = Session()
            current.sport = sport.group(1)
        elif current:
            for field, attribute in Fields.items():
                regexp = '\s+%s: (.+)' % field
                match = re.match(regexp, line)
                if match:
                    setattr(current, attribute, match.group(1))
                    break
    if current:
        sessions.append(current)
    return sessions
    
if __name__ == '__main__':
    sessions = parse_email(fileinput.input())
    possibilities = calculate_prices(sessions)
    for price in sorted(possibilities):
        for seats in possibilities[price]:
            print '%10.2f : %s' % (price, ', '.join(seats))