Automat

What it is and what it does

Automat is a finite-state machine library that lets you define stateful behavior using Python method calls and type protocols, rather than requiring you to pass generic input objects through a state engine. Instead of scattering conditional logic across methods to track state flags, you declare states and transitions upfront, and the library synthesizes a clean interface that enforces valid state sequences at runtime.

The library targets the common pattern where your code needs to behave differently depending on its state (like a coffee machine that should only brew when it has water, beans, and a closed lid), but your callers should not need to know or care that you've implemented it as a state machine. It depends only on typing_extensions and supports Python 3.9 through 3.13, with full type hints throughout.

Use it for:

• Implement protocol-based state machines for complex objects like network connections, protocol handlers, or device controllers that need strict state ordering.
• Build workflow engines or task schedulers where transitions between states must be explicit and validated at definition time.
• Create deterministic finite-state transducers that transform input sequences into output behaviors while maintaining clean, method-call-based APIs.
• Model state-dependent behavior in game logic, UI state management, or embedded systems where invalid state combinations must be impossible.
• Define type-safe state machines for async systems where each state transition can trigger side effects or return computed results.

Worth the install?

AI-flagged interpretation of the facts on this page — verify before relying

Automat provides a Python library for building finite-state machines using type-safe, method-based interfaces rather than generic input/output objects, letting you organize stateful behavior while keeping a clean API.

Yes, if you need to model stateful behavior with strict state ordering and want a clean, type-safe API. The permissive MIT license and low install friction make it low-risk. However, the 485-day gap since the last release suggests the project is aging; verify that it meets your Python version requirements (3.9+) and that its approach fits your use case before committing to it as a core dependency.

Install

automat on PyPI

pip install automat

uv add automat

poetry add automat

Installing Automat

Before you install

Low install friction with a single lightweight runtime dependency (typing_extensions). Maintenance status is aging—last release was 485 days ago, though the repository remains active with a recent commit on 2026-01-13 and 647 stars.

License in practice

MIT license (permissive) allows free use, modification, and distribution with minimal restrictions, making it suitable for both open-source and commercial projects.

Quickstart

from automat import TypeMachineBuilder
from typing import Protocol

class MyStateMachine(Protocol):
    def event(self) -> None: pass

builder = TypeMachineBuilder(MyStateMachine, CoreData)
state_a = builder.state("state_a")
state_b = builder.state("state_b")
state_a.upon(MyStateMachine.event).to(state_b).returns(None)
machine = builder.build()

Requires Python 3.9 or later; familiarity with typing.Protocol and state machine concepts recommended.

Verify before relying

• Whether the library is actively maintained or in maintenance-only mode given the 485-day gap since last release
• Performance characteristics and scalability limits for complex state machines with many states or transitions
• Real-world adoption patterns and whether it integrates well with async/await workflows

Package facts

Evidence: automat-25.4.16-py3-none-any.whl

Keywords: fsm, state machine, automata

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