python-injection

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

• Easy to use
• No impact on class and function definitions
• 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