10 thoughts on “Let’s Learn Python #19 – Finite-State Machines (FSM)”

1. Thanks for creating this! It helped me understand the concept better. cheers!

2. if only i knew this earlier. imagine having to programme this in linear fashion…

3. Great tutorial, but I have a problem, could you help me please? I keep getting this error:
   File "C:Python27RobotMaid_FSM.py", line 143, in <module>
   r = RobotMaid()
   File "C:Python27RobotMaid_FSM.py", line 129, in _init_
   self.FSM.AddState("Sleep", Sleep(self.FSM))
   AttributeError: 'FSM' object has no attribute 'AddState'

   Please any help would be very much appreciated. Thank you.

4. Hi Trevor, Thanks for this video it was really helpful. As i am building a FSM for one of my projects…
   I tried implementing the code but i keep getting this error: self.FSM.AddState("Sleep",Sleep(self.FSM))
   AttributeError: 'FSM' object has no attribute 'AddState'

   i checked for spelling but everything seems fine. Could you help please?

5. Hey,Trevor. I want to ask. Why I just showing "Transitioning…" when I run the code. Where i had created mistakes. Thank you very much
   from random import randint
   from time import clock

   ##=======================================
   State = type("State", (object,), {})

   class LightOn(State):
   def Execute(self):
   print ("Light is On!")

   class LightOff(State):
   def Execute(self):
   print ("Light is Off!")

   ##=======================================

   class Transition(object):
   def __init__(self, toState):
   self.toState = toState

   def Execute(self):
   print ("Transitioning…")

   ##=======================================

   class SimpleFSM(object):
   def __init__(self, char):
   self.char = char
   self.states = {}
   self.transitions = {}
   self.curState = None
   self.trans = None

   def SetState(self, stateName):
   self.curState = self.states[stateName]

   def Transition(self, transName):
   self.trans = self.transitions[transName]

   def Execute(self):
   if (self.trans):
   self.trans.Execute()
   self.SetState(self.trans.toState)
   self.trans = None
   self.curState.Execute

   ##=======================================

   class Char(object):
   def __init__(self):
   self.FSM = SimpleFSM(self)
   self.LightOn = True

   ##=======================================

   if _name_ == "__main__":
   light = Char()

   light.FSM.states["On"] = LightOn()
   light.FSM.states["Off"] = LightOff()
   light.FSM.transitions["toOn"] = Transition("On")
   light.FSM.transitions["toOff"] = Transition("Off")

   light.FSM.SetState("On")

   for i in range(20):
   startTime = clock()
   timeInterval = 1
   while (startTime + timeInterval > clock()):
   pass
   if (randint(0,2)):
   if (light.LightOn):
   light.FSM.Transition("toOff")
   light.LightOn = False
   else:
   light.FSM.Transition("toOn")
   light.LightOn = True
   light.FSM.Execute()

6. My mind is about to explode. Too much work.

7. No sarcasm in the starting in this video?

8. Hey Trevor, I like your video. I have a small bit of feedback: For your actual code, you might find that using a monospaced font makes it easier to read.

9. Hello! Thanks for an really nice tutorial, but I have one question (If you see this)

   If I would want to have multiple robot maids with unique IDs (As in the book "Programming Game AI by Example"), should I make the Char an actual class and have it produce A unique ID for each?
   Or should I simply make a Dictionary in the main function that stores each object with a unique ID assigned as the Key?

   Which would you recommend?

10. just in case:

    from random import randint
    
    import time

    #creating a class with type
    
    ######################################################################
    
    State = type("State",(object,),{})

    class LightOn(State):
    
    def Execute(self):
    
    print('the light is on')
    
    class LightOff(State):
    
    def Execute(self):
    
    print('the light is off')
    
    #############################################
    
    ##transition###################

    class transition(object):
    
    def __init__(self,toState):
    
    self.toState = toState

    def Execute(self):
    
    print("Transition")
    
    ###############################################
    
    #################creating FSm###############################
    
    class simpleFSM(object):
    
    def __init__(self,char):
    
    self.char = char
    
    self.states = {}
    
    self.transitions = {}
    
    self.curState = None
    
    self.trans = None

    def SetState(self,stateName):
    
    self.curState = self.states[stateName]

    def Transition(self,transName):
    
    self.trans = self.transitions[transName]

    def Execute(self):
    
    if(self.trans):
    
    self.trans.Execute()
    
    self.SetState(self.trans.toState)
    
    self.trans = None
    
    self.curState.Execute()

    #############################character class################

    class char(object):
    
    def __init__(self):
    
    self.FSM = simpleFSM(self)
    
    self.LightOn = True

    if __name__=="__main__":
    
    light = char()
    
    light.FSM.states["On"] = LightOn()
    
    light.FSM.states["Off"] = LightOff()
    
    light.FSM.transitions["toOn"] = transition("On")
    
    light.FSM.transitions["toOff"] = transition("Off")

    light.FSM.SetState("On")

    for i in range(5):
    
    startTime = time.perf_counter()
    
    timeInterval = 1
    
    while startTime+timeInterval>time.perf_counter():
    
    pass
    
    if randint(0,2):
    
    if light.LightOn:
    
    light.FSM.Transition("toOff")
    
    light.LightOn = False
    
    else:
    
    light.FSM.Transition("toOn")
    
    light.LightOn = True
    
    light.FSM.Execute()

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