Two Envelopes

envelopes.py

#!/usr/bin/python
import random

nonSwitcherMoney = 0
switcherMoney = 0

def random_amount_of_money(): return 1 + 999 * random.random()
def coin_flip(): return random.random() > 0.5

# do a million trials
for i in xrange(1000000):

	# pick an amount in the smaller envelope, X
	X = random_amount_of_money()

	# randomly pick an envelope to give to the player
	player_received_smaller = coin_flip()

	if player_received_smaller:
		nonSwitcherMoney += X
		switcherMoney += 2.0 * X
	else:
		nonSwitcherMoney += 2.0 * X
		switcherMoney += X

print "Non Switcher Money:", nonSwitcherMoney
print "Always-Switch Money:", switcherMoney