pysm

pysm - Python State Machine

Versatile and flexible Python State Machine library.

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Implement simple and complex state machines

It can do simple things like this:

.. image:: https://cloud.githubusercontent.com/assets/3026621/15031178/bf5efb2a-124e-11e6-9748-0b5a5be60a30.png

Or somewhat more complex like that:

.. image:: https://cloud.githubusercontent.com/assets/3026621/15031148/ad955f06-124e-11e6-865e-c7e3340f14cb.png

Python State Machine

The State Pattern <https://en.wikipedia.org/wiki/State_pattern>_ solves many problems, untangles the code and saves one's sanity. Yet.., it's a bit rigid and doesn't scale. The goal of this library is to give you a close to the State Pattern simplicity with much more flexibility. And, if needed, the full state machine functionality, including FSM <https://en.wikipedia.org/wiki/Finite-state_machine>, HSM <https://en.wikipedia.org/wiki/UML_state_machine #Hierarchically_nested_states>, PDA <https://en.wikipedia.org/wiki/Pushdown_automaton>_ and other tasty things.

Goals

• Provide a State Pattern-like behavior with more flexibility (see Documentation <http://pysm.readthedocs.io/en/latest/examples.html>_ for examples)
• Be explicit and don't add any magic code to objects that use pysm
• Handle directly any kind of event or input (not only strings) - parsing strings is cool again!
• Keep it simple, even for someone who's not very familiar with the FSM terminology

Features

• Finite State Machine (FSM)
• Hierarchical State Machine (HSM) with Internal/External/Local transitions
• Pushdown Automaton (PDA)
• Transition callbacks - action, before, after
• State hooks - enter, exit, and other event handlers
• Entry and exit actions are associated with states, not transitions
• Events may be anything as long as they're hashable
• States history and transition to previous states
• Conditional transitions (if/elif/else-like logic)
• Explicit behaviour (no method or attribute is added to the object containing a state machine)
• No need to extend a class with State Machine class (composition over inheritance)
• Fast (even with hundreds of transition rules)
• Not too many pythonisms, so that it's easily portable to other languages (ie. JavaScript <https://github.com/pgularski/smjs>_).
• Micropython support

Installation

Install pysm from PyPI <https://pypi.python.org/pypi/pysm/>_::

pip install pysm

or clone the Github pysm repository <https://github.com/pgularski/pysm/>_::

git clone https://github.com/pgularski/pysm
cd pysm
python setup.py install

Documentation

Read the docs for API documentation and examples - http://pysm.readthedocs.io/

See Unit Tests to see it working and extensively tested.

Micropython support

The library works with pyboards!::

import upip upip.install('upysm')

Links

• Documentation <http://pysm.readthedocs.io>_
• Installation <http://pysm.readthedocs.io/en/latest/installing.html>_
• Github <https://github.com/pgularski/pysm>_
• Issues <https://github.com/pgularski/pysm/issues>_
• Examples <http://pysm.readthedocs.io/en/latest/examples.html>_