"计算函数内的尝试次数"

Question

我对 Python 还是很陌生，对为什么我的尝试计数器没有增加感到困惑。

def start_game():
    print("\nWelcome to A Python Game")
    print("Choose one of the following:")
    print("1) Play game")
    print("2) About")
    print("3) Quit")
    firstchoice()

def firstchoice():
    max_attempts = 3
    attempts = 0
    while attempts < max_attempts:
        choice = input("> ")
        if choice == "1":
            game()
        elif choice == "2":
            gameabout()
        elif choice == "3":
            return None
        else:
            attempts =+ 1
            print("Invalid choice.")
            print("Attempts to successfully get past the main menu: ", attempts)

start_game()