pysm 0.3.1

Python State Machine

Python State Machine

The 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, HSM, PDA and other tasty things.

Goals

• Provide a State Pattern-like behavior with more flexibility

• Be explicit and don’t add any code to objects

• Handle directly any kind of event (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).

Installation

Install pysm from PyPI:

pip install pysm

or clone the Github pysm repository:

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

Documentation

Read the docs - http://pysm.readthedocs.io/

Links

• Documentation

• Installation

• Github

• Issues

• Examples