dependencies

7.7.1 verified Mon Apr 27 auth: no python

A Python library for constructor injection designed with OOP in mind. Current version 7.7.1. It uses a simple decorator-based API to inject dependencies into class constructors, supporting type hints and aliases. Release cadence is irregular.

pip install dependencies

Common errors

error dependencies.errors.DependencyError: 'Logger' is not registered. ↓

cause Missing binding for 'Logger' class.

fix

Add binder.bind(Logger, value(Logger())) inside your configure function.

error AttributeError: 'Inject' object has no attribute 'configure' ↓

cause Using `Inject` as a decorator instead of instantiating.

fix

Change @Inject to container = Inject(); container.configure(...).

error TypeError: __init__() missing 1 required positional argument: 'logger' ↓

cause Using `This()` without type hint or incorrect usage.

fix

Add type hint: def __init__(self, logger: Logger = This()):

error RecursionError: maximum recursion depth exceeded ↓

cause Circular dependency between classes.

fix

Refactor to break the cycle or use This(lazy=True) for one of the dependencies.

Warnings

gotcha Inject must be used as a class instance, not a decorator. Common mistake: decorating with @Inject instead of instantiating and calling configure. ↓

fix Use `container = Inject(); container.configure(...)` instead of `@Inject`.

breaking In version 6.x, `Inject` was a decorator. In 7.x, it became a class. Import paths changed. ↓

fix Use `from dependencies import Inject` (class). Code using `@inject` must be rewritten.

deprecated Using `This()` with non-type-hinted arguments may be deprecated in future versions. ↓

fix Always provide type hints for parameters using `This()`.

gotcha When using `autoload=False`, you must explicitly configure all dependencies. Common mistake: forgetting to bind a dependency leads to `DependencyError`. ↓

fix Bind all dependencies with `binder.bind(...)` inside `configure` function.

gotcha Circular dependencies are not detected automatically and cause recursion errors. ↓

fix Avoid circular references or use lazy injection with `This(lazy=True)`.

Imports

Inject
```
from dependencies import Inject
```
This
```
from dependencies import This
```
value
```
from dependencies import value
```

Quickstart

Basic dependency injection setup: bind implementations and get instances.

from dependencies import Inject, This, value

class Logger:
    pass

class Database:
    def __init__(self, logger: Logger = This()):
        self.logger = logger

def configure(binder):
    db = Database()
    binder.bind(Database, value(db))
    binder.bind(Logger, value(Logger()))

container = Inject(autoload=False)
container.configure(configure)
db = container.instance(Database)
print(db.logger.__class__.__name__)  # Logger