移动互联网的终端包括我们大家经常使用的,网站网页的优化方法,wordpress移动应用,教做年糕博客网站什么是状态机#xff1f;
关键属性#xff1a; 状态和转换
状态#xff1a; 系统当前状态
转换#xff1a;一种状态到另外一种状态的变化。
转换由触发事件或是条件启动。
状态机-状态图
状态机使用场景#xff1a;
自动售货机 电梯 交通灯 组合锁 停车计时…什么是状态机
关键属性 状态和转换
状态 系统当前状态
转换一种状态到另外一种状态的变化。
转换由触发事件或是条件启动。
状态机-状态图
状态机使用场景
自动售货机 电梯 交通灯 组合锁 停车计时器
使用state_machine 模块创建状态机第一步使用acts_as_state_machine装饰器
acts_as_state_machine class Process: initial 属性值设置为 True
created State(initialTrue)
waiting State()
running State()
terminated State()
blocked State()
swapped_out_waiting State()
swapped_out_blocked State()
定义转换。在 state_machine 模块中转换是 Event 类的一个实例。我们使用 参数 from_states 和 to_state 定义可能的转换。
wait Event(from_states(created,
running,
blocked,
swapped_out_waiting),
to_statewaiting)
run Event(from_stateswaiting,
to_staterunning)
terminate Event(from_statesrunning,
to_stateterminated)
block Event(from_states(running,swapped_out_blocked),
to_stateblocked)
swap_wait Event(from_stateswaiting,
to_stateswapped_out_waiting)
swap_block Event(from_statesblocked,
to_stateswapped_out_blocked) from_states 可以是单个状态也可以是一组状态元组。 state_machine 模块为我们 提供了 before 和 after 装饰器二者可以分别用于在转换发生之前或之后执行操作。你可以 想象在系统中更新一些对象或者向某人发送电子邮件或通知。在本例中操作仅限于打印关于 进程状态更改的信息。
transition() 函数它接受三个参数 process Process 的一个实例 event Event 的一个实例 wait 、 run 、 terminate 等 event_name 事件的名称。
执行事件时出错则输出事件的名称。 下面是 transition() 函数的代码
def transition(process, event, event_name):
try:
event()
except InvalidStateTransition as err:
print(fError: transition of {process.name}
from {process.current_state} to {event_name} failed)
state_info() 函数显示进程当前激活状态的一些基本信息。 def state_info(process):
print(fstate of {process.name}: {process.current_state})
在 main() 函数的开头我们定义了一些字符串常量它们被作为 event_name 传递。
def main():
RUNNING running
WAITING waiting
BLOCKED blocked
TERMINATED terminated
创建两个 Process 实例并展示它们的初始状态信息。 p1, p2 Process(process1), Process(process2)
[state_info(p) for p in (p1, p2)] 允许的转换应该与 状态图相关。例如应该可以从一个运行状态切换到一个阻塞状态但是不应该从一个阻塞状态 切换到一个运行状态。
from state_machine import (State,Event,acts_as_state_machine,after,before,InvalidStateTransition)acts_as_state_machine
class Process:createdState(initialTrue) # 创建状态waitingState() #等待状态runningState()# 运行状态terminatedState()# 停止状态blockedState() # 阻塞swapper_out_waitingState()#swapper_out_blockedState()# 等待状态 转入的状态from_states 目标状态 to_statewaitEvent(from_states(created,running,blocked,swapper_out_waiting),to_statewaiting)runEvent(from_stateswaiting,to_staterunning)terminateEvent(from_statesrunning,to_stateterminated)blockEvent(from_states(running,swapper_out_blocked),to_stateblocked)swap_waitEvent(from_stateswaiting,to_stateswapper_out_waiting)swap_blockEvent(from_statesblocked,to_stateswapper_out_blocked)def __init__(self,name):self.namenameafter(wait)def wait_info(self):print(f{self.name} entered waiting mode)after(run)def run_info(self):print(f{self.name} is running)before(ternimate)def terminate_info(self):print(f{self.name} terminated)after(block)def block_info(self):print(f{self.name} is blocked)after(swap_wait)def swap_wait_info(self):print(f{self.name} is swapped out and waiting)after(swap_block)def swap_block_info(self):print(f{self.name} is swapped out and blocked)after(block)def block_info(self):print(f{self.name} is blocked)after(swap_wait)def swap_wait_info(self):print(f{self.name} is swapped out and waiting)after(swap_block)def swap_block_info(self):print(f{self.name} is swapped out and blocked)def transition(process,event,event_name):try:event()except InvalidStateTransition as err:print(fError: transaction of {process.name} from {process.current_state} to {event_name} failed)# 显示信息def state_info(process):print(fstate of {process.name}:{process.current_state})def main():RUNNINGrunningWAITINGwaitingBLOCKEDblockedTERMINATEDterminatedp1,p2Process(process1),Process(process2)[state_info(p) for p in (p1,p2)]print(-------1----------)transition(p1,p1.wait,WAITING)transition(p2,p2.terminate,TERMINATED)[state_info(p) for p in (p1,p2)]print(------2----------)transition(p1,p1.run,RUNNING)transition(p2,p2.wait,WAITING)[state_info(p) for p in (p1, p2)]print(------3----------)transition(p2, p2.run, RUNNING)[state_info(p) for p in (p1, p2)]print(------4----------)[transition(p,p.block,BLOCKED) for p in (p1,p2)][state_info(p) for p in (p1, p2)]print(------5----------)[transition(p, p.terminate, TERMINATED) for p in (p1, p2)]if __name____main__:main()state of process1:created
state of process2:created
-------1----------
process1 entered waiting mode
Error: transaction of process2 from created to terminated failed
state of process1:waiting
state of process2:created
------2----------
process1 is running
process2 entered waiting mode
state of process1:running
state of process2:waiting
------3----------
process2 is running
state of process1:running
state of process2:running
------4----------
process1 is blocked
process1 is blocked
process2 is blocked
process2 is blocked
state of process1:blocked
state of process2:blocked
------5----------
Error: transaction of process1 from blocked to terminated failed
Error: transaction of process2 from blocked to terminated failed
