FunDI mastering

Learn how to use FunDI like a pro (or at least fake it convincingly).

FunDI is a lightweight library with a focused codebase — smaller than big frameworks like aiogram or FastAPI, but carefully crafted to solve dependency injection in a clean, composable way.

So, let’s begin our tour with basic definitions:

• Dependency — function that is used to create and/or provide data.

• Configurable dependency — function that when called creates dependency that will be injected. These should be used for more complex scenarios, or generic dependencies that work based on context.

• Lifespan-dependency — function that creates data, provides it and cleans up resources. This is a simple Python generator function with exactly one yield, used to manage setup and teardown.

• Dependant — function that uses other functions as dependencies. Can also be used as dependency.

• Scope — injection start-up environment.

• Injection — process of resolving function arguments from scope and its dependencies.

• Side effect — a function that is injected before a dependant. Unlike normal dependencies, its result is not passed to the dependant.

• Hook — a function that is called on certain events with a predefined set of positional parameters. Hooks can affect injection behavior.

Deep dive to each component

• Dependency
  • Naming convention
• Lifespan dependency
  • Generator-function lifespan dependency
  • Context-manager lifespan dependency
  • Exception awareness
  • When to use lifespan dependencies
• Configurable dependency(factory)
  • Composite dependencies
  • Dependency configuration
• Dependant
• Scope
  • Creating a Scope
  • Adding Values
  • Adding Typed Instances
  • Adding Type Factories
  • Updating a Scope
  • Resolving Dependencies
  • Working with Legacy Scopes
  • Merging Scopes
• Injection
  • Own exit stack
  • Dependency parameter awareness
  • Summary
• Side effects
  • Global side effect
  • Local side effect
• Hooks
  • Graph hook
  • Scope hook
  • Combining hooks
• Overriding
• Debugging
  • Exceptions