ALT-event-system

A lightweight, flexible publish-subscribe event system for Python applications.

Overview

ALT-event-system provides a simple yet powerful event-driven architecture that enables loose coupling between components through an event bus pattern. Perfect for building reactive applications, plugin systems, or any scenario where you need decoupled communication.

Features

• 🚀 Simple API - Easy to understand and use
• 🎯 Type-safe - Full type hints for better IDE support
• 🔌 Loose Coupling - Components communicate without direct dependencies
• 🌟 Wildcard Subscriptions - Subscribe to all events with *
• 📜 Event History - Track and query past events
• 🛡️ Error Isolation - Handler errors don't affect other handlers
• 🔍 Source Tracking - Optional source identification for events
• ⚡ Zero Dependencies - Uses only Python standard library

Installation

pip install ALT-event-system

Quick Start

from alt_event_system import EventSystem

# Create an event system
events = EventSystem()

# Define a handler
def on_user_login(event):
    print(f"User {event.data['user_id']} logged in from {event.data['ip']}")

# Subscribe to events
events.subscribe("user.login", on_user_login)

# Emit events
events.emit("user.login", {"user_id": 123, "ip": "192.168.1.1"})

Advanced Usage

Wildcard Subscriptions

Subscribe to all events:

def log_all_events(event):
    print(f"[{event.timestamp}] {event.type}: {event.data}")

events.subscribe("*", log_all_events)

Event History

Track and query past events:

# Get recent events
history = events.get_history(limit=10)

# Filter by event type
login_events = events.get_history(event_type="user.login")

Error Handling

Handler errors are isolated:

def safe_handler(event):
    print("I still work even if others fail!")

events.subscribe("test.event", safe_handler)

API Reference

• EventSystem() - Create a new event system
• subscribe(event_type, handler) - Subscribe to events
• emit(event_type, data, source=None) - Emit an event
• get_history(event_type=None, limit=100) - Get event history
• clear_history() - Clear event history
• get_subscriber_count(event_type) - Count subscribers

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

Author

Avi Layani - avilayani@gmail.com

License

This project is licensed under the MIT License - see the LICENSE file for details.