Welcome to incant🪄!

incant is a Python open source library for composing and calling functions. Dependency injection is but one of many use-cases served well by incant; wrapping functions with context managers for observability is another.

incant includes support for:

• a convenience layer with a simple API, based on a powerful and fast performance layer

• a very flexible system for matching dependencies using inspect.Parameter, including the parameter name, type annotation and default value

• sync and async functions and dependencies

• sync and async context manager dependencies

• no global state

• attaching arbitrary external dependencies to functions (forced dependencies), commonly used for side-effects

incant has a very lean API surface, the core API being:

• a single class, incant.Incanter, for keeping state (dependency rules)

• a method for registering dependencies, Incanter.register_hook(), and a number of higher level, more user-friendly helpers (Incanter.register_by_name(), Incanter.register_by_type())

• methods for calling arbitrary functions while composing them with their dependencies, Incanter.compose_and_call() and its async variant, Incanter.acompose_and_call()

• methods for invoking arbitrary functions while picking and forwarding any required arguments, Incanter.incant() and its async variant, Incanter.aincant()

• methods for composing functions in advance, without calling them, Incanter.compose()

• methods for adjusting arbitrary functions to arbitrary parameters, Incanter.adapt()

incant is able to leverage runtime type annotations but is also capable of functioning without them. incant is also fully type-annotated for use with Mypy and smart editors.

The Tutorial contains a walkthough and some real-life use cases of incant.

If you’re coming from a pytest background, incant dependency factories are roughly equivalent to pytest fixtures.

Installation

To install incant, simply:

$ pip install incant