Question

I am trying to simulate the scoring of a squash game using english rules.
These are:

• Only the server is awarded a point if they win a rally.
• If the server wins a rally, they receive a point and continue as server.
• If the returner wins a rally, they become the server but don’t receive a point.
• The first player to reach 9 points wins the game unless the score has reached 8-8.
• If the score reaches 8-8, the player who reached 8 first decides whether to play to 9 or to 10.

The code I have is this:

import random

def eng_game(a,b):
    A = 'bob'
    B = 'susie'
    players = [A, B]

    server = random.choice(players)
    print server

    points_bob = 0
    points_susie= 0

    prob_A_wins = 0.4
    prob_B_wins = 0.6

    while points_bob or points_susie < 9:
        probability = random.random()
        print probability
        if probability < prob_A_wins and server == A:
            points_bob += 1
        elif probability < prob_A_wins and server == B:
            server == A
            print server

        if probability > prob_A_wins and server == B:
            points_susie += 1
        elif probability > prob_A_wins and server == A:
            server == B
            print server

        print points_bob
        print points_susie

This code returns that Susie wins 9-0 when in some cases the server should be swapped to Bob to win the point, but this doesn’t happen. The serve stays with Susie and she wins the point.

Answer 1

I think the issue is the statements server == A and server == B should be server = A and server = B so that assignment takes place instead of a comparison.

Another edge case bug I see is if probability ends up exactly 0.4 your program will act like that virtual serve never took place.

I would change your loop to:

while points_bob < 9 and points_susie < 9:
    probability = random.random()
    print probability
    if probability <= prob_A_wins and server == A:
        points_bob += 1
    elif probability <= prob_A_wins and server == B:
        server = A
        print server

    if probability > prob_A_wins and server == B:
        points_susie += 1
    elif probability > prob_A_wins and server == A:
        server = B
        print server

    print points_bob
    print points_susie