Python State Machine

Github | PyPI

pysm is a tiny, explicit hierarchical state machine library. The classic core remains dependency-free and suitable for small runtimes, while optional modules provide run-to-completion event scheduling, thread-safe dispatch, async dispatch, serialization, builder ergonomics, and shipped type information for editors and type checkers.

The core runtime still follows the original composition-first style: create states, add them to a root machine, add transitions, initialize the machine, and dispatch hashable events. Newer helpers are layered around that core instead of changing the top-level import.

Core imports stay small:

from pysm import StateMachine, State, Event

Advanced behavior is opt-in:

from pysm.queued import QueuedStateMachine
from pysm.queued import ThreadSafeQueuedStateMachine
from pysm.aio import AsyncQueuedStateMachine
from pysm.serialization import snapshot, restore
from pysm.builder import StateMachineBuilder

• Module documentation
  • Public imports
  • Core
  • Queued runtime
  • Async runtime
  • Serialization
  • Builder
• Optional Modules
  • Core vs Optional Modules
  • Core Behavior Updates
  • Initial Entry Events
  • Queued Run-To-Completion Dispatch
  • Thread-Safe Queued Dispatch
  • Async Queued Dispatch
  • Typed Packages
  • Snapshot And Restore
  • Builder
  • MicroPython / upysm
• Installation
  • Building the documentation locally
• Examples
  • Simple state machine
  • Fluent builder
  • Complex hierarchical state machine
  • Different ways to attach event handlers
  • Reverse Polish notation calculator
  • Queued dispatch
  • Async dispatch
  • Snapshot and restore