添加另一个状态变量来跟踪游戏的一般状态，并在用户按下K_1时更改它。

run = True
game_state = "menu"
while run:
  if game_state == "menu":
    if keys[pygame.K_1]:
      # clean up sprites or whatnot
      game_state = "playing"
  elif game_state == "playing":
     if keys[pygame.K_LEFT]:  # ...

没有什么说你不能把你的游戏分成多个主循环，但是，如果这对你来说更简单的话。

def handle_menu():
    while True:
        # draw menu, handle menu input, etc.
        if keys[pygame.K_1]:
             return 1  # assume this means 1 player
        if keys[pygame.K_2]:
             return 2  # assume this means 2 players

def handle_game(player_count):
    while True:
        # draw actual game, etc.

def main():
    player_count = handle_menu()
    handle_game(player_count)