labthings_fastapi.descriptors.property

Define an object to represent an Action, as a descriptor.

Module Contents

Classes

PropertyDescriptor

A property that can be accessed via the HTTP API

API

class labthings_fastapi.descriptors.property.PropertyDescriptor(model: type, initial_value: Any = None, readonly: bool = False, observable: bool = False, description: Optional[str] = None, title: Optional[str] = None, getter: Optional[Callable] = None, setter: Optional[Callable] = None)

A property that can be accessed via the HTTP API

By default, a PropertyDescriptor is “dumb”, i.e. it acts just like a normal variable.

Initialization

model: type[pydantic.BaseModel]

None

readonly: bool

False

__set_name__(owner, name: str)

property title

A human-readable title

property description

A description of the property

__get__(obj, type=None) → Any

The value of the property

If obj is none (i.e. we are getting the attribute of the class), we return the descriptor.

If no getter is set, we’ll return either the initial value, or the value from the object’s dict, i.e. we behave like a variable.

If a getter is set, we will use it, unless the property is observable, at which point the getter is only ever used once, to set the initial value.

__set__(obj, value)

Set the property’s value

_observers_set(obj)

A set used to notify changes

emit_changed_event(obj: labthings_fastapi.thing.Thing, value: Any) → None

Notify subscribers that the property has changed

NB this function must be run from a thread, not the event loop.

async emit_changed_event_async(obj: labthings_fastapi.thing.Thing, value: Any)

Notify subscribers that the property has changed

property name

The name of the property

add_to_fastapi(app: fastapi.FastAPI, thing: labthings_fastapi.thing.Thing)

Add this action to a FastAPI app, bound to a particular Thing.

property_affordance(thing: labthings_fastapi.thing.Thing, path: Optional[str] = None) → labthings_fastapi.thing_description.model.PropertyAffordance

Represent the property in a Thing Description.

getter(func: Callable) → typing_extensions.Self

set the function that gets the property’s value

setter(func: Callable) → typing_extensions.Self

Decorator to set the property’s value

PropertyDescriptors are variabes - so they will return the value they hold when they are accessed. However, they can run code when they are set: this decorator sets a function as that code.