问题：有一个糖果公司需要设计一个糖果售卖机，控制流程如下图，需要怎么实现？
这是一个状态图，每个圆圈都是一种状态。很明显，有有25分钱、 没有25分钱、 售出糖果、 糖果售罄四个状态，同时也对应四个动作：投入25分钱，退回25分钱，转动曲柄和发放糖果。
那如何从状态图得到真正的代码呢？
简单代码实现如下：
#! -*- coding: utf-8 -*- class GumballMachine: # 找出所有状态，并创建实例变量来持有当前状态，然后定义状态的值 STATE_SOLD_OUT = 0 STATE_NO_QUARTER = 1 STATE_HAS_QUARTER = 2 STATE_SOLD = 3 state = STATE_SOLD_OUT def __init__(self, count=0): self.count = count if count > 0: self.state = self.STATE_NO_QUARTER def __str__(self): return "Gumball machine current state: %s" % self.state def insert_quarter(self): # 投入25分钱 if self.state == self.STATE_HAS_QUARTER: # 如果已经投过 print("You can't insert another quarter") elif self.state == self.STATE_NO_QUARTER: # 如果没有投过 self.state = self.STATE_HAS_QUARTER print("You inserted a quarter") elif self.state == self.STATE_SOLD_OUT: # 如果已经售罄 print("You can't insert a quarter, the machine is sold out") elif self.state == self.STATE_SOLD: # 如果刚刚买了糖果 print("Please wait, we're already giving you a gumball") def eject_quarter(self): # 退回25分 if self.state == self.STATE_HAS_QUARTER: print("Quarter returned") self.state = self.STATE_NO_QUARTER elif self.state == self.STATE_NO_QUARTER: print("You haven't inserted a quarter") elif self.state == self.STATE_SOLD: print("Sorry, you alread turned the crank") elif self.state == self.SOLD_OUT: print("You can't eject, you haven't inserted") def turn_crank(self): # 转动曲柄 if self.state == self.STATE_SOLD: print("Turning twice doesn't get you another gumball") elif self.state == self.STATE_NO_QUARTER: print("You turned but there's no quarter") elif self.state == self.STATE_SOLD_OUT: print("You turned, but there are no gumballs") elif self.state == self.STATE_HAS_QUARTER: print("You turned...") self.state = self.STATE_SOLD self.dispense() def dispense(self): # 发放糖果 if self.state == self.STATE_SOLD: print("A gumball comes rolling out the slot") self.count -= 1 if self.count == 0: self.state = self.STATE_SOLD_OUT else: self.state = self.STATE_NO_QUARTER elif self.state == self.STATE_NO_QUARTER: print("You need to pay first") elif self.state == self.STATE_SOLD_OUT: print("No gumball dispensed") elif self.state == self.STATE_HAS_QUARTER: print("No gumball dispensed") if __name__ == "__main__": # 以下是代码测试 gumball_machine = GumballMachine(5) # 装入5 个糖果 print(gumball_machine) gumball_machine.insert_quarter() # 投入25分钱 gumball_machine.turn_crank() # 转动曲柄 print(gumball_machine) gumball_machine.insert_quarter() #投入25分钱 gumball_machine.eject_quarter() # 退钱 gumball_machine.turn_crank() # 转动曲柄 print(gumball_machine) gumball_machine.insert_quarter() # 投入25分钱 gumball_machine.turn_crank() # 转动曲柄 gumball_machine.insert_quarter() # 投入25分钱 gumball_machine.turn_crank() # 转动曲柄 gumball_machine.eject_quarter() # 退钱 print(gumball_machine) 这段代码有几个问题：
...