2d6+a vs. 2d6+b Probability Simulator

2d6-opposed-probability.py

import random

def main():
    trials = 1000000
    print_each_trial = False
    reroll_if_tie = True
    print('A', 'B', 'A%', 'B%', 'Tie%', sep='\t')
    for a_mod in range(-3, 3 + 1):
        for b_mod in range(-3, 3 + 1):
            results = {'a' : 0, 'b' : 0, 'tie' : 0}
            for t in range(trials):
                while True: # reroll-if-Tie loop
                    a = _2d6() + a_mod
                    b = _2d6() + b_mod
                    if (print_each_trial):
                        print ("{0} vs. {1}: ".format(a, b), end='')
                    if (a == b):
                        if (print_each_trial):
                            print("Tie.", end='')
                        if (reroll_if_tie):
                            if (print_each_trial):
                                print(" Rerolling.")
                            continue
                        if (print_each_trial):
                            print()
                        results['tie'] += 1
                    elif (a > b):
                        if (print_each_trial):
                            print ("A wins.")
                        results['a'] += 1
                    elif (b > a):
                        if (print_each_trial):
                            print("B wins.")
                        results['b'] += 1
                    else:
                        assert False, "Logically impossible"
                    break # reroll-if-Tie loop
            results_probabilities = {k: v / trials for k, v in results.items()}
            print(a_mod, b_mod, results_probabilities['a'], results_probabilities['b'], results_probabilities['tie'], sep='\t')

def _2d6():
    return random.randint(1, 6) + random.randint(1, 6)

if __name__ == "__main__":
    main()