python-injection

Installation

⚠️ Requires Python 3.12 or higher

pip install python-injection

Features

• Automatic dependency resolution based on type hints.
• Support for multiple dependency lifetimes: transient, singleton, constant, and scoped.
• Works seamlessly in both async and sync environments.
• Separation of dependency sets using modules.
• Runtime switching between different sets of dependencies.
• Centralized setup logic using entrypoints.
• Built-in type annotation for easy integration with FastAPI.
• Lazy dependency resolution for optimized performance.

Motivations

1. Easy to use
2. No impact on class and function definitions
3. No tedious configuration

Quick start

Simply apply the decorators and the package takes care of the rest.

from injection import injectable, inject, singleton

@singleton
class Printer:
    def __init__(self):
        self.history = []

    def print(self, message: str):
        self.history.append(message)
        print(message)

@injectable
class Service:
    def __init__(self, printer: Printer):
        self.printer = printer

    def hello(self):
        self.printer.print("Hello world!")

@inject
def main(service: Service):
    service.hello()

if __name__ == "__main__":
    main()

Resources

⚠️ The package isn't threadsafe by default, for better performance in single-threaded applications and those using asyncio.

Non-threadsafe functions are those that resolve dependencies or define scopes. They all come with an optional parameter threadsafe.

You can set PYTHON_INJECTION_THREADSAFE=1 in environment variables to make the package fully threadsafe. The environment variable is resolved at the Python module level, so be careful if the variable is defined dynamically.

• Basic usage
• Scoped dependencies
• Testing
• Advanced usage
• Loaders
• Entrypoint
• Integrations
  • FastAPI
  • What if my framework isn't listed?
• Concrete example