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def | __init__ (self, name) |
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def | __repr__ (self) |
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def | __str__ (self) |
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def | cleanup (self) |
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def | defaultEnter (self, *args) |
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def | defaultExit (self) |
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def | defaultFilter (self, request, args) |
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def | demand (self, request, *args) |
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def | filterOff (self, request, args) |
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def | forceTransition (self, request, *args) |
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def | getCurrentFilter (self) |
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def | getCurrentOrNextState (self) |
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def | getCurrentStateOrTransition (self) |
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def | getStateChangeEvent (self) |
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def | isInTransition (self) |
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def | request (self, request, *args) |
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def | requestNext (self, *args) |
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def | requestPrev (self, *args) |
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def | setBroadcastStateChanges (self, doBroadcast) |
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def | setStateArray (self, stateArray) |
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def | accept (self, event, method, extraArgs=[]) |
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def | acceptOnce (self, event, method, extraArgs=[]) |
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def | addTask (self, *args, **kwargs) |
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def | detectLeaks (self) |
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def | doMethodLater (self, *args, **kwargs) |
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def | getAllAccepting (self) |
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def | ignore (self, event) |
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def | ignoreAll (self) |
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def | isAccepting (self, event) |
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def | isIgnoring (self, event) |
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def | removeAllTasks (self) |
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def | removeTask (self, taskOrName) |
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A Finite State Machine. This is intended to be the base class
of any number of specific machines, which consist of a collection
of states and transitions, and rules to switch between states
according to arbitrary input data.
The states of an FSM are defined implicitly. Each state is
identified by a string, which by convention begins with a capital
letter. (Also by convention, strings passed to request that are
not state names should begin with a lowercase letter.)
To define specialized behavior when entering or exiting a
particular state, define a method named enterState() and/or
exitState(), where "State" is the name of the state, e.g.::
def enterRed(self):
... do stuff ...
def exitRed(self):
... cleanup stuff ...
def enterYellow(self):
... do stuff ...
def exitYellow(self):
... cleanup stuff ...
def enterGreen(self):
... do stuff ...
def exitGreen(self):
... cleanup stuff ...
Both functions can access the previous state name as
self.oldState, and the new state name we are transitioning to as
self.newState. (Of course, in enterRed(), self.newState will
always be "Red", and the in exitRed(), self.oldState will always
be "Red".)
Both functions are optional. If either function is omitted, the
state is still defined, but nothing is done when transitioning
into (or out of) the state.
Additionally, you may define a filterState() function for each
state. The purpose of this function is to decide what state to
transition to next, if any, on receipt of a particular input. The
input is always a string and a tuple of optional parameters (which
is often empty), and the return value should either be None to do
nothing, or the name of the state to transition into. For
example::
def filterRed(self, request, args):
if request in ['Green']:
return (request,) + args
return None
def filterYellow(self, request, args):
if request in ['Red']:
return (request,) + args
return None
def filterGreen(self, request, args):
if request in ['Yellow']:
return (request,) + args
return None
As above, the filterState() functions are optional. If any is
omitted, the defaultFilter() method is called instead. A standard
implementation of defaultFilter() is provided, which may be
overridden in a derived class to change the behavior on an
unexpected transition.
If self.defaultTransitions is left unassigned, then the standard
implementation of defaultFilter() will return None for any
lowercase transition name and allow any uppercase transition name
(this assumes that an uppercase name is a request to go directly
to a particular state by name).
self.state may be queried at any time other than during the
handling of the enter() and exit() functions. During these
functions, self.state contains the value None (you are not really
in any state during the transition). However, during a transition
you *can* query the outgoing and incoming states, respectively,
via self.oldState and self.newState. At other times, self.state
contains the name of the current state.
Initially, the FSM is in state 'Off'. It does not call enterOff()
at construction time; it is simply in Off already by convention.
If you need to call code in enterOff() to initialize your FSM
properly, call it explicitly in the constructor. Similarly, when
`cleanup()` is called or the FSM is destructed, the FSM transitions
back to 'Off' by convention. (It does call enterOff() at this
point, but does not call exitOff().)
To implement nested hierarchical FSM's, simply create a nested FSM
and store it on the class within the appropriate enterState()
function, and clean it up within the corresponding exitState()
function.
There is a way to define specialized transition behavior between
two particular states. This is done by defining a from<X>To<Y>()
function, where X is the old state and Y is the new state. If this
is defined, it will be run in place of the exit<X> and enter<Y>
functions, so if you want that behavior, you'll have to call them
specifically. Otherwise, you can completely replace that transition's
behavior.
See the code in SampleFSM.py for further examples.