python-singleton-patterns

🧠

A clean collection of Python Singleton implementations — from basics to thread-safe and async-compatible versions.

Singleton is a classic design pattern that ensures a class has only one instance, providing a global point of access.
In this repository, you'll find multiple real-world Singleton implementations in Python — including solutions for inheritance, multithreading, and asynchronous environments.

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🚀 Features

✅ Simple and intuitive examples
✅ Supports inheritance via metaclass
✅ Thread-safe implementation
✅ Fully async-compatible Singleton
✅ Easy to test and extend

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📂 File Structure

python-singleton-patterns/
├── singleton_basic.py             # Classic Singleton using __new__
├── singleton_inheritance.py      # Inheritable Singleton using Metaclass
├── singleton_threadsafe.py       # Thread-safe Singleton with Lock
├── singleton_async.py            # Async Singleton for asyncio
├── singleton_test.py             # Unified test runner for all versions
├── requirements.txt              # (Optional) Dependencies if needed
└── README.md                     # You're here.

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🔧 How to Use

Clone the repo and run the tests:

git clone https://github.com/your-username/python-singleton-patterns.git
cd python-singleton-patterns
python singleton_test.py

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🧪 Quick Overview

Basic Singleton

from singleton_basic import Singleton

a = Singleton()
b = Singleton()
print(a is b)  # True

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Singleton with Inheritance

from singleton_inheritance import Singleton

class Service(Singleclass):
    pass

s1 = Service()
s2 = Service()
print(s1 is s2)  # True

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Thread-Safe Singleton

from singleton_threadsafe import Singleton

s1 = Singleton()
s2 = Singleton()
print(s1 is s2)  # Always True (even in threads)

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Async Singleton

from singleton_async import AsyncSingleton
import asyncio

async def run():
    a = await AsyncSingleton()
    b = await AsyncSingleton()
    print(a is b)  # True

asyncio.run(run())

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✅ Test Output

Sample from singleton_test.py:

🔹 Testing Basic Singleton
[Basic] a is b: True

🔹 Testing Inheritance-Safe Singleton (Metaclass)
[Inheritance] a is b: True

🔹 Testing Thread-Safe Singleton
[Thread-safe] Unique instance count: 1
[Thread-safe] All instances are the same: True

🔹 Testing Async Singleton
[Async] Unique instance count: 1
[Async] All async instances are the same: True

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📚 Concepts Covered

• __new__() vs __call__() in metaclasses
• Python metaclass mechanics
• threading.Lock for thread-safety
• asyncio.Lock for async contexts
• Singleton-friendly inheritance

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🖖 Contributions

Pull requests and forks are welcome!
If you find a new use-case or edge-case Singleton, feel free to add it.

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📜 License

This project is licensed under the MIT License.
Use freely, modify boldly.

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⭐️ If you liked it...

Don’t forget to Star 🌟 the repository to help others find it.

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