python-injection

Project motivations

Dependency injection in Python has long been a source of frustration.

Existing solutions are often verbose, require extensive boilerplate, or fail to leverage Python's type hints effectively. python-injection was created to solve these problems once and for all by providing a simple, elegant, and powerful dependency injection framework that feels natural to Python developers.

The goal is straightforward: make dependency injection so easy that you'll wonder how you ever managed without it.

Why choose python-injection?

• Type-driven resolution: Dependencies are automatically resolved using Python's type annotations.
• Decorator-based registration: Register your dependencies with simple, readable decorators.
• Flexible lifetimes: Choose from four types of lifetimes to match your needs:
  • Transient: A new instance every time
  • Singleton: One instance for the entire application
  • Scoped: One instance per scope, with context manager support
  • Constant: A value created once and never re-resolved, either pre-existing or computed lazily
• Profile support: Ability to swap certain dependencies based on a profile.
• Pull-based instantiation: Dependencies registered with decorators are only created when needed, improving startup time and resource usage.
• Full sync/async support: Works seamlessly with both synchronous and asynchronous code.

Installation

Requires Python 3.12 or higher.

pip install python-injection

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()