Metadata-Version: 1.1
Name: pyeds
Version: 0.7.3
Summary: Python Event Driven System
Home-page: https://github.com/nradulovic
Author: Nenad Radulovic
Author-email: nenad.b.radulovic@gmail.com
License: LGPL
Description: **Python Event Driven System**
        
        .. contents:: Table of contents
           :backlinks: top
           :local:
        
        Introduction
        ============
        
        This package provides a system allows to efficiently write finite state machines 
        (FSM) by hand. The focus was to make the API as simplest as possible since no 
        GUI tools are included to define a FSM.
        
        Installation
        ============
        
        PyEDS can be installed using the standard Python tool ``pip`` with
        
        .. code-block:: console
        
            pip install pyeds
        
        How to use it
        =============
        
        The basic routine to create a state machine is the following:
         1) Declare a FSM class 
         2) Declare all state classes
         3) Instantiate FSM class
         
        Declaring a FSM class
        ---------------------
        
        FSM class is the entry point of a FSM which is used to receive events (see 
        below) and do the transitions between states. Each FSM must declare it's own 
        class which is a subclass of ``StateMachine``. The simplest way is to just
        declare an empty class which inherits the class ``StateMachine``:
        
        .. code:: python
        
            from pyeds import fsm
            
            class MyFsm(fsm.StateMachine):
                pass
           
        Declaring a state class
        -----------------------
        
        Each state is represented by different class. Every method in that class may 
        handle one particular event. To declare the state, a class must be decorated 
        with ``DeclareState`` decorator which require state machine as an argument. 
        This decorator binds the state class to the specific FSM class. Also, the new 
        state class must be a subclass of ``State`` class:
        
        .. code:: python
        
            @fsm.DeclareState(MyFsm)
            class MyState(fsm.State):
                pass
                
        Declare a new class per state.
            
        Instantiating the FSM
        ---------------------
        
        To instantiate the FSM class do the following:
        
        .. code:: python
        
            my_fsm = MyFsm()
            
        After object initialization the FSM is put into running state.
        
        Blinky example
        ==============
        
        The following is an example of FSM which is called Blinky. The FSM will print 
        'on' text and 'off' text on console with 0.5 seconds of delay between the 
        messages. 
        
        The Blinky FSM has 2 states:
         - State On
         - State Off
         
        ::
        
            o----+
                 |
             On  v                Off
            +----+----+  blink   +---------+
            |         +--------->+         |
            |         |          |         |
            |         +<---------+         |
            +---------+  blink   +---------+
        
        
        The event ``blink`` is used to trigger transitions between the states.
        
        .. code:: python
        
            from pyeds import fsm
        
        
            # The first step is to declare a class which represent custom FSM.
                
            class BlinkyFsm(fsm.StateMachine):
                pass
        
        
            # The second step is to start writing the states of new state machine:
        
            @fsm.DeclareState(BlinkyFsm)
            class Initialization(fsm.State):
                def on_init(self):
                    fsm.Every(0.5, fsm.Event('blink')
                    return StateOn
                    
                    
            @fsm.DeclareState(BlinkFsm)
            class StateOn(fsm.State):
                def on_entry(self):
                    print('on')
                    
                def on_blink(self, event):
                    return StateOff
                    
                    
            @fsm.DeclareState(BlinkFsm)
            class StateOff(fsm.State):
                def on_entry(self):
                    print('off')
                        
                def on_blink(self, event):
                    return StateOn
        
        
            # The final step is to instantiate the FSM class defined in the first step.
        
            blinky_fsm = BlinkyFsm()
        
        After creation the FSM is automatically put into a running state.
        
        Event
        =====
        
        An event is a notable occurrence at a particular point in time. Events can, but
        do not necessarily, cause state transitions from one state to another in state 
        machines
        
        An event can have associated parameters, allowing the event to convey not only 
        the occurrence but also quantitative information about the occurrence. 
        
        An event in PyEDS is instanced using class ``Event``. 
        
        The associated parameters with an event are:
         - name of the event
         - producer of event
         
        Generate an event
        -----------------
        
        To generate a new event just instantiate ``Event`` class with event name as
        parameter:
        
        .. code:: python
        
            new_event = fsm.Event('my_special_event')
        
        Alternative way is to first declare a new event class and instantiate this
        derive class:
        
        .. code:: python
        
            class MySpecialEvent(fsm.Event):
                pass
                
            new_event = MySpecialEvent() # This event is implicitly called 'my_special_event'
        
        In this case base ``Event`` class will implicitly take the name of the class as 
        own name. This can be overriden by calling the super constructor:
        
        .. code:: python
        
            # This event has the exact same name as the above one
            class MySecondEvent(fsm.Event):
                def __init__(self):
                    super().__init__('my_special_event')
        
            # Another way of creating event with same name as above events
            class MyThirdEvent(fsm.Event):
                name = 'my_special_event'
        
        Event class attributes and methods
        ----------------------------------
        
        Attributes:
         - ``self.name`` - this is a string containing event name
         - ``self.producer`` - specifies which state machine has generated this event.
         
        Methods:
         - ``release(self)`` - this method is called by state machine when it has 
           finished the processing of the event
         - ``execute(self, handler)`` - this method is called by state machine and it 
           is used to modify how an event handler is called.
        
        Rules about event naming
        ------------------------
        
        When an event is created and sent to a state machine it's name is used to decide
        which method in current state instance should be invoked. The state machine 
        takes the name of the event, it prepends text ``on_`` to the name string and 
        then it looks up to event handler method.
        
        Example: If an event named ``toggle`` is created and sent to a state machine, 
        the target state machine will lookup for a method named ``on_toggle`` in the 
        current state instance. 
        
        Since the event name directly impacts which state instance method will be called
        the name of events must follow the Python identifier naming rules. 
        
        A Python identifier starts with a letter A to Z or a to z or an underscore (_) 
        followed by zero or more letters, underscores and digits (0 to 9). Python does 
        not allow punctuation characters such as @, $, and % within identifiers. 
        
        .. code:: python
        
            ok_event = fsm.Event('some_event_with_long_name')
            bad_event = fsm.Event('you cannot use spaces, @, $ and % here')
        
        State
        =====
        
        A state is a description of the status of a system that is waiting to execute 
        a transition.
        
        State attributes and methods
        ----------------------------
        
        Attributes:
         - ``self.name`` - this is a string containing state name
         - ``self.producer`` - specifies which state machine has this state
         - ``self.sm`` - the same as ``self.producer`` but shorter
         - ``self.logger`` - this is the logger which is used by state machine
         - ``self.rm`` - this is ResourceManager for this state
         - ``super_state`` - this is a class attribute that specifies super 
           state class
         
        Methods:
         - ``release(self)`` - this method is called by state machine just before
           state machine termination
         - ``on_entry(self)`` - this method is called by state machine when it has
           entered the state
         - ``on_exit(self)`` - this method is called by state machine when it has
           exited the state
         - ``on_init(self)`` - this method is called by state machine when it has
           entered the state and now needs to initialize the state
         - ``on_unhandled_event`` - this method is called by state machine when
           no event handlers where found for this state
           
        State machine
        =============
        
        State machine attributes and methods
        ------------------------------------
        
        Attributes:
         - ``self.name`` - this is a string containing Sstate machine name
         - ``self.logger`` - this is the logger which is used by state machine
         - ``self.rm`` - this is ResourceManager for this state machine
         - ``self.state`` - current state of this machine
         
        Methods:
         - ``run(self)`` - this is state machine dispatch method
         - ``put(self, event)`` - this method puts an event to state machine wait
           queue
         - ``terminate(self)`` - pend termination of the state machine. After 
           exiting this method the state machine may still run. Use ``self.wait``
           to wait for FSM termination
         - ``wait(self)`` - wait for FSM to terminate
         - ``instance_of`` - get the instance of a state class
         - ``on_terminate`` - gets called by state machine just before termination
         - ``on_exception`` - gets called when unhandled exception has occured
         
        State transition
        ================
        
        Switching from one state to another is called state transition. A transition is 
        a set of actions to be executed when a condition is fulfilled or when an event 
        is received.
        
        Transitions are started by returning target state class in an event handler.
        
        .. code:: python
         
            def on_some_event(self, event):
                do_some_stuff()
                return SomeOtherState # Note: return a class object, not instance object
        
        Hierarchical Finite State Machines (HFSM)
        =========================================
        
        Please, refer to Wikipedia article for further explanation: 
         - https://en.wikipedia.org/wiki/UML_state_machine#Hierarchically_nested_states 
        
        Source
        ======
        
        Source is available at github:
         - https://github.com/nradulovic/pyeds
        
Keywords: fsm hsm state finite event machine
Platform: UNKNOWN
Classifier: Development Status :: 3 - Alpha
Classifier: License :: OSI Approved :: GNU Lesser General Public License v3 (LGPLv3)
Classifier: Programming Language :: Python :: 3.4
Classifier: Topic :: Software Development
