Spooky Shuffle game for MouseHunt Halloween 2014

SpookyShuffle.py

import random
ROUNDS = 1000000

def play():
	unopen = [n/2 for n in range(18) ]
	opened = []
	tickets = 0
	while len(unopen) > 0 :
		x = random.randint(0, len(unopen) - 1)
		if unopen[x] in opened:
			opened.remove(unopen[x])
			del unopen[x]
		else:
			while True:
				y = random.randint(0, len(unopen) - 1)
				if x != y:
					break
			first = unopen[x]
			second = unopen[y]
			if first == second:
				unopen = [n for n in unopen if n != first]
			else:
				tickets += 1;
				unopen.remove(first)
				unopen.remove(second)
				opened.extend([first, second])

	return tickets

results = [0]*9
for i in range(ROUNDS):
	results[play()] += 1

cumulative = 0.0
average = 0

for ticket, val in enumerate(results):
	chance = float(val) / ROUNDS * 100
	cumulative += chance
	average += ticket * float(val) / ROUNDS
	print str(ticket) + ':', val, "%0.2f" % chance + '%', '(' +  "%0.2f" % cumulative + '%)'

print "Average:", average