TSignal

TSignal is a lightweight, pure-Python signal/slot library that provides thread-safe, asyncio-compatible event handling inspired by the Qt signal/slot pattern—but without the heavyweight Qt dependencies. It enables clean decoupling of components, seamless thread-to-thread communication, and flexible asynchronous/synchronous slot handling.

Key Features

• Pure Python: No Qt or external GUI frameworks needed.
• Async/Await Friendly: Slots can be synchronous or asynchronous, and integrate seamlessly with asyncio.
• Thread-Safe: Signal emissions and slot executions are automatically managed for thread safety.
• Flexible Connection Types: Direct or queued connections, automatically chosen based on the caller and callee threads.
• Worker Thread Pattern: Simplify background task execution with a built-in worker pattern that provides an event loop and task queue in a dedicated thread.
• Familiar Decorators: Inspired by Qt’s pattern, @t_with_signals, @t_signal, and @t_slot let you define signals and slots declaratively.

Why TSignal?

Modern Python applications often rely on asynchronous operations and multi-threading. Traditional event frameworks either require large external dependencies or lack seamless async/thread support. TSignal provides:

• A minimal, dependency-free solution for event-driven architectures.
• Smooth integration with asyncio for modern async Python code.
• Automatic thread-affinity handling so cross-thread signals "just work."
• Decorator-based API that’s intuitive and maintainable.

Installation

TSignal requires Python 3.10 or higher.

git clone https://github.com/TSignalDev/tsignal-python.git
cd tsignal-python
pip install -e .

For development (includes tests and linting tools):

pip install -e ".[dev]

Quick Start

Basic Example

from tsignal import t_with_signals, t_signal, t_slot

@t_with_signals
class Counter:
    def __init__(self):
        self.count = 0
    
    @t_signal
    def count_changed(self):
        pass
    
    def increment(self):
        self.count += 1
        self.count_changed.emit(self.count)

@t_with_signals
class Display:
    @t_slot
    async def on_count_changed(self, value):
        print(f"Count is now: {value}")

# Connect and use
counter = Counter()
display = Display()
counter.count_changed.connect(display, display.on_count_changed)
counter.increment()  # Will print: "Count is now: 1"

Asynchronous Slot Example

@t_with_signals
class AsyncDisplay:
    @t_slot
    async def on_count_changed(self, value):
        await asyncio.sleep(1)  # Simulate async operation
        print(f"Count updated to: {value}")

# Usage in async context
async def main():
    counter = Counter()
    display = AsyncDisplay()
    
    counter.count_changed.connect(display, display.on_count_changed)
    counter.increment()
    
    # Wait for async processing
    await asyncio.sleep(1.1)

asyncio.run(main())

Core Concepts

Signals and Slots

• Signals: Declared with @t_signal. Signals are attributes of a class that can be emitted to notify interested parties.
• Slots: Declared with @t_slot. Slots are methods that respond to signals. Slots can be synchronous or async functions.
• Connections: Use signal.connect(receiver, slot) to link signals to slots. Connections can also be made directly to functions or lambdas.

Thread Safety and Connection Types

TSignal automatically detects whether the signal emission and slot execution occur in the same thread or different threads:

• Direct Connection: If signal and slot share the same thread affinity, the slot is invoked directly.
• Queued Connection: If they differ, the call is queued to the slot’s thread/event loop, ensuring thread safety.

This mechanism frees you from manually dispatching calls across threads.

Worker Threads

For background work, TSignal provides a @t_with_worker decorator that:

• Spawns a dedicated event loop in a worker thread.
• Allows you to queue async tasks to this worker.
• Enables easy start/stop lifecycle management.
• Integrates with signals and slots for thread-safe updates to the main

Worker Example

from tsignal import t_with_worker, t_signal

@t_with_worker
class DataProcessor:
    @t_signal
    def processing_done(self):
        """Emitted when processing completes"""

    async def run(self, *args, **kwargs):
        # The main entry point for the worker thread’s event loop
        # Wait for tasks or stopping signal
        await self._tsignal_stopping.wait()

    async def process_data(self, data):
        # Perform heavy computation in the worker thread
        result = await heavy_computation(data)
        self.processing_done.emit(result)

processor = DataProcessor()
processor.start()

# Queue a task to run in the worker thread:
processor.queue_task(processor.process_data(some_data))

# Stop the worker gracefully
processor.stop()

Documentation and Example

• Usage Guide: Learn how to define signals/slots, manage threads, and structure your event-driven code.
• API Reference: Detailed documentation of classes, decorators, and functions.
• Examples: Practical use cases, including UI integration, async operations, and worker pattern usage.
• Logging Guidelines: Configure logging levels and handlers for debugging.
• Testing Guide: earn how to run tests and contribute safely.

Logging

Configure logging to diagnose issues:

import logging
logging.getLogger('tsignal').setLevel(logging.DEBUG)

For more details, see the Logging Guidelines.

Testing

TSignal uses pytest for testing:

# Run all tests
pytest

# Run with verbose output
pytest -v

# Run specific test file
pytest tests/unit/test_signal.py

See the Testing Guide for more details.

Contributing

We welcome contributions. Please read the Contributing Guidelines before submitting PRs.

License

TSignal is licensed under the MIT License. See LICENSE for details.