StateLogic

StateLogic doesn’t just manage state. It protects it.

A pure, safe, and elegant finite state machine for Python — with colored terminal logging.

StateLogic is a lightweight, dependency-free finite state machine library that enforces correctness by design.

It was born from frustration with existing FSM libraries that allow invalid states, silent failures, or require complex boilerplate. StateLogic fixes all of that — and adds beautiful colored logging as a bonus.

Design Philosophy — Why StateLogic Is Different (and Better)

"A state machine must never lie about its state."

StateLogic is built on four unbreakable principles:

1. The current state can only be changed via a valid, registered transition

Direct assignment like fsm.state("HACKED") is silently ignored if the state is not part of a defined transition.
This prevents bugs, race conditions, and security issues in critical systems.

2. You cannot set an initial state before defining transitions

fsm = StateLogic()
fsm.state("SOLID")        # → Does nothing (no transitions defined yet)
fsm.state()               # → None

Only after you define at least one transition are states considered "valid":

fsm.transition("melts", "SOLID", "LIQUID")
fsm.state("SOLID")        # → Now allowed

3. Invalid transitions are impossible — not just undetected

If you try to go from GAS → SOLID without defining that path, nothing happens.
No exception (unless you want one), no silent success — just correctness.

4. Hooks are first-class: before, on, and after

fsm.before("melts", lambda: input("Melt? ") == "Y")
fsm.on("melts", lambda: print("Melting started..."))
fsm.after("melts", lambda: print("Now it's water!"))

This isn't just convenience — it's enforced lifecycle safety.

These rules make StateLogic ideal for:

• Embedded systems
• Game logic
• Workflow engines
• Protocol implementations
• Any domain where state corruption is unacceptable

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Installation

pip install statelogic

Quick Example

from statelogic import StateLogic

s = StateLogic()
s.author("Wilgat").appName("WaterFSM").majorVersion(1)

# Define valid physics
s.transition("freeze",     "LIQUID", "SOLID")
s.transition("melts",      "SOLID",  "LIQUID")
s.transition("evaporate",  "LIQUID", "GAS")
s.transition("condense",   "GAS",    "LIQUID")

# Try to cheat physics
s.state("PLASMA")          # → Ignored. Still None.
print(s.state())           # → None

# Now play by the rules
s.transition("sublimate", "SOLID", "GAS")  # Define the edge case
s.state("SOLID")           # → Now allowed
s.sublimate()
print(s.state())           # → GAS

s.infoMsg("Sublimation complete!", "SCIENCE")

Output (with colors):

2025-12-02 10:30:45.123456 WaterFSM(v1.0.0)  [SCIENCE]: 
  Sublimation complete!

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Features

• Zero dependencies
• Python 2.7 and 3.6+ compatible
• Beautiful colored terminal logging (infoMsg, safeMsg, criticalMsg)
• Full hook system: before, on, after
• Dynamic attributes via Attr class
• Signal handling (Ctrl+C → graceful exit)
• Shell & environment utilities
• 100% test coverage

Hook Examples

before — Guard transitions

def confirm():
    return input("Proceed? (y/n): ").lower() == "y"

s.before("launch", confirm)
s.launch()   # Only runs if user says yes

on — React immediately

s.on("error", lambda: s.criticalMsg("System failure!", "ALERT"))

after — Cleanup or notify

s.after("shutdown", lambda: s.safeMsg("System offline.", "BYE"))

Project Links

• Python: https://github.com/Wilgat/Statelogic
• PyPI: https://pypi.org/project/statelogic/
• TypeScript version: https://github.com/Wilgat/StateSafe
• npm: https://www.npmjs.com/package/statesafe

License

MIT © Wilgat

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StateLogic doesn’t just manage state. It protects it.