coin.py

#!/bin/env python3
import sys
import random

if not len(sys.argv) == 4:
    print("usage:", sys.argv[0], "reps points a-win-%")
    sys.exit(1)

reps = int(sys.argv[1])
points = int(sys.argv[2])
wp = int(sys.argv[3])

# number of set wins
a_wins = 0
b_wins = 0

for i in range(reps):
    # current points in the set
    ap = 0
    bp = 0
    while True:
        if random.randrange(100) < wp:
            ap += 1
            if ap >= points and ap - bp >= 2: break
        else:
            bp += 1
            if bp >= points and bp - ap >= 2: break
    if ap > bp: a_wins += 1
    else: b_wins += 1

print("a %wins", a_wins * 100 / reps)
print("b %wins", b_wins * 100 / reps)