lightbulb.di.conditions

class DependencyExpression(order: Sequence[BaseCondition], required: bool)

A cached dependency expression. This contains the steps needed to resolve the dependencies for a single function parameter.

Parameters:

• order – The sequence of conditions required to resolve the dependency expression.

• required – Whether the dependency expression is required - i.e. can resolve to None.

classmethod create(expr: Any, /) → DependencyExpression[Any]

Create a dependency expression from a type expression (type hint).

Parameters:

expr – The type expression to create the dependency expression from.

Returns:

The created dependency expression.

async resolve(container: container_.Container, /) → T | None

Resolve the dependency that satisfies this expression from the given container.

Parameters:

container – The container to use while satisfying the expression.

Returns:

The resolved dependency, or None if the dependency could not be resolved, and required was True upon creation.

class If(inner: type[Any] | UnionType | tuple[Any, ...] | None)

Dependency injection condition that will only fall back when the requested dependency is not known to the current container. This is the default when no condition is specified.

Example

@lightbulb.di.with_di
async def foo(bar: If[Bar] | None) -> None:
    # The 'bar' parameter will be 'None' if the 'Bar' dependency
    # is unregistered.
    ...

# Lightbulb treats the lack of meta annotation as meaning the same as 'If[dep]'
@lightbulb.di.with_di
async def foo(bar: Bar | None) -> None:
    # Same as previous example
    ...

class Try(inner: type[Any] | UnionType | tuple[Any, ...] | None)

Dependency injection condition that will fall back when the requested dependency is either unknown to the current container, or creation raises an exception.

Example

@lightbulb.di.with_di
async def foo(bar: Try[Bar] | None) -> None:
    # The 'bar' parameter will be 'None' if creating the 'Bar' dependency
    # failed, or is unregistered.
    ...