API Reference

exception labthings.ActionKilledException

Sibling of SystemExit, but specific to thread termination.

class labthings.ClientEvent

An event-signaller object with per-client setting and waiting.

A client can be any Greenlet or native Thread. This can be used, for example, to signal to clients that new data is available

clear() → bool

Clear frame event, once processed.

set(timeout=5)

Signal that a new frame is available.

Parameters

timeout – (Default value = 5)

wait(timeout: int = 5)

Wait for the next data frame (invoked from each client’s thread).

Parameters

timeout – int: (Default value = 5)

class labthings.CompositeLock(locks, timeout: int = - 1)

Class that behaves like a labthings.core.lock.StrictLock, but allows multiple locks to be acquired and released.

Parameters

  • locks (list) – List of parent RLock objects

  • timeout (int) – Time in seconds acquisition will wait before raising an exception

acquire(blocking: bool = True, timeout=<object object>)
Parameters

  • blocking – (Default value = True)

  • timeout – (Default value = sentinel)

class labthings.LabThing(app: Optional[flask.app.Flask] = None, id_: Optional[str] = None, prefix: str = '', title: str = '', description: str = '', version: str = '0.0.0', types: Optional[List[str]] = None, format_flask_exceptions: bool = True, external_links: bool = True, json_encoder=<class 'labthings.json.encoder.LabThingsJSONEncoder'>)

The main entry point for the application. You need to initialize it with a Flask Application:

>>> app = Flask(__name__)
>>> labthing = labthings.LabThing(app)

Alternatively, you can use init_app() to set the Flask application after it has been constructed.

Parameters

  • app (flask.Flask) – the Flask application object

  • prefix (str) – Prefix all routes with a value, eg v1 or 2010-04-01

  • title (str) – Human-readable title of the Thing

  • description (str) – Human-readable description of the Thing

  • version (str) – Version number of the Thing

  • types (list of str) – List of Thing types, used by clients to filter discovered Things

  • format_flask_exceptions (bool) – JSON format all exception responses

  • external_links (bool) – Use external links in Thing Description where possible

  • json_encoder – JSON encoder class for the app

add_component(component_object, component_name: str)

Add a component object to the LabThing, allowing it to be used by extensions and other views by name, rather than reference.

Parameters

  • device_object – Component object

  • device_name – str: Component name, used by extensions to find the object

Parameters

  • view –

  • rel –

  • kwargs – (Default value = None)

  • params – (Default value = None)

add_view(view: Type[labthings.views.View], *urls: str, endpoint: Optional[str] = None, **kwargs)

Adds a view to the api.

Parameters

  • view – View class

  • urls (str) – one or more url routes to match for the resource, standard flask routing rules apply. Any url variables will be passed to the resource method as args.

  • endpoint (str) – endpoint name (defaults to Resource.__name__() Can be used to reference this route in fields.Url fields

  • kwargs – kwargs to be forwarded to the constructor of the view.

Additional keyword arguments not specified above will be passed as-is to flask.Flask.add_url_rule().

Examples:

labthing.add_view(HelloWorld, '/', '/hello')
labthing.add_view(Foo, '/foo', endpoint="foo")
labthing.add_view(FooSpecial, '/special/foo', endpoint="foo")
property description: str

Human-readable description of the Thing

emit(event_type: str, data: dict)

Find a matching event type if one exists, and emit some data to it

Parameters

  • event_type – str:

  • data – dict:

init_app(app)

Initialize this class with the given flask.Flask application. :param app: the Flask application or blueprint object

Examples::

labthing = LabThing() labthing.add_view(…) labthing.init_app(app)

register_extension(extension_object: labthings.extensions.BaseExtension)

Add an extension to the LabThing. This will add API views and lifecycle functions from the extension to the LabThing

Parameters

extension_object (labthings.extensions.BaseExtension) – Extension instance

property safe_title: str

Lowercase title with no whitespace

property title: str

Human-readable title of the Thing

url_for(view: Type[labthings.views.View], **values)

Generates a URL to the given resource. Works like flask.url_for().

Parameters

  • view –

  • values –

property version: str

Version number of the Thing

view(*urls: str, **kwargs)

Wraps a labthings.View class, adding it to the LabThing. Parameters are the same as add_view().

Example:

app = Flask(__name__)
labthing = labthings.LabThing(app)

@labthing.view('/properties/my_property')
class Foo(labthings.views.PropertyView):
    schema = labthings.fields.String()

    def get(self):
        return 'Hello, World!'
class labthings.Schema(*, only: Optional[Union[Sequence[str], Set[str]]] = None, exclude: Union[Sequence[str], Set[str]] = (), many: bool = False, context: Optional[Dict] = None, load_only: Union[Sequence[str], Set[str]] = (), dump_only: Union[Sequence[str], Set[str]] = (), partial: Union[bool, Sequence[str], Set[str]] = False, unknown: Optional[str] = None)

Base schema class with which to define custom schemas.

Example usage:

import datetime as dt
from dataclasses import dataclass

from marshmallow import Schema, fields


@dataclass
class Album:
    title: str
    release_date: dt.date


class AlbumSchema(Schema):
    title = fields.Str()
    release_date = fields.Date()


album = Album("Beggars Banquet", dt.date(1968, 12, 6))
schema = AlbumSchema()
data = schema.dump(album)
data  # {'release_date': '1968-12-06', 'title': 'Beggars Banquet'}
Parameters

  • only – Whitelist of the declared fields to select when instantiating the Schema. If None, all fields are used. Nested fields can be represented with dot delimiters.

  • exclude – Blacklist of the declared fields to exclude when instantiating the Schema. If a field appears in both only and exclude, it is not used. Nested fields can be represented with dot delimiters.

  • many – Should be set to True if obj is a collection so that the object will be serialized to a list.

  • context – Optional context passed to fields.Method and fields.Function fields.

  • load_only – Fields to skip during serialization (write-only fields)

  • dump_only – Fields to skip during deserialization (read-only fields)

  • partial – Whether to ignore missing fields and not require any fields declared. Propagates down to Nested fields as well. If its value is an iterable, only missing fields listed in that iterable will be ignored. Use dot delimiters to specify nested fields.

  • unknown – Whether to exclude, include, or raise an error for unknown fields in the data. Use EXCLUDE, INCLUDE or RAISE.

Changed in version 3.0.0: prefix parameter removed.

Changed in version 2.0.0: __validators__, __preprocessors__, and __data_handlers__ are removed in favor of marshmallow.decorators.validates_schema, marshmallow.decorators.pre_load and marshmallow.decorators.post_dump. __accessor__ and __error_handler__ are deprecated. Implement the handle_error and get_attribute methods instead.

class Meta

Options object for a Schema.

Example usage:

class Meta:
    fields = ("id", "email", "date_created")
    exclude = ("password", "secret_attribute")

Available options:

  • fields: Tuple or list of fields to include in the serialized result.

  • additional: Tuple or list of fields to include in addition to the

    explicitly declared fields. additional and fields are mutually-exclusive options.

  • include: Dictionary of additional fields to include in the schema. It is

    usually better to define fields as class variables, but you may need to use this option, e.g., if your fields are Python keywords. May be an OrderedDict.

  • exclude: Tuple or list of fields to exclude in the serialized result.

    Nested fields can be represented with dot delimiters.

  • dateformat: Default format for Date <fields.Date> fields.

  • datetimeformat: Default format for DateTime <fields.DateTime> fields.

  • timeformat: Default format for Time <fields.Time> fields.

  • render_module: Module to use for loads <Schema.loads> and dumps <Schema.dumps>.

    Defaults to json from the standard library.

  • ordered: If True, order serialization output according to the

    order in which fields were declared. Output of Schema.dump will be a collections.OrderedDict.

  • index_errors: If True, errors dictionaries will include the index

    of invalid items in a collection.

  • load_only: Tuple or list of fields to exclude from serialized results.

  • dump_only: Tuple or list of fields to exclude from deserialization

  • unknown: Whether to exclude, include, or raise an error for unknown

    fields in the data. Use EXCLUDE, INCLUDE or RAISE.

  • register: Whether to register the Schema with marshmallow’s internal

    class registry. Must be True if you intend to refer to this Schema by class name in Nested fields. Only set this to False when memory usage is critical. Defaults to True.

OPTIONS_CLASS

alias of marshmallow.schema.SchemaOpts

dump(obj: Any, *, many: Optional[bool] = None)

Serialize an object to native Python data types according to this Schema’s fields.

Parameters

  • obj – The object to serialize.

  • many – Whether to serialize obj as a collection. If None, the value for self.many is used.

Returns

Serialized data

New in version 1.0.0.

Changed in version 3.0.0b7: This method returns the serialized data rather than a (data, errors) duple. A ValidationError is raised if obj is invalid.

Changed in version 3.0.0rc9: Validation no longer occurs upon serialization.

dumps(obj: Any, *args, many: Optional[bool] = None, **kwargs)

Same as dump(), except return a JSON-encoded string.

Parameters

  • obj – The object to serialize.

  • many – Whether to serialize obj as a collection. If None, the value for self.many is used.

Returns

A json string

New in version 1.0.0.

Changed in version 3.0.0b7: This method returns the serialized data rather than a (data, errors) duple. A ValidationError is raised if obj is invalid.

error_messages: Dict[str, str] = {}

Overrides for default schema-level error messages

fields: Dict[str, marshmallow.fields.Field]

Dictionary mapping field_names -> Field objects

classmethod from_dict(fields: Dict[str, Union[marshmallow.fields.Field, type]], *, name: str = 'GeneratedSchema') → type

Generate a Schema class given a dictionary of fields.

from marshmallow import Schema, fields

PersonSchema = Schema.from_dict({"name": fields.Str()})
print(PersonSchema().load({"name": "David"}))  # => {'name': 'David'}

Generated schemas are not added to the class registry and therefore cannot be referred to by name in Nested fields.

Parameters

  • fields (dict) – Dictionary mapping field names to field instances.

  • name (str) – Optional name for the class, which will appear in the repr for the class.

New in version 3.0.0.

get_attribute(obj: Any, attr: str, default: Any)

Defines how to pull values from an object to serialize.

New in version 2.0.0.

Changed in version 3.0.0a1: Changed position of obj and attr.

handle_error(error: marshmallow.exceptions.ValidationError, data: Any, *, many: bool, **kwargs)

Custom error handler function for the schema.

Parameters

  • error – The ValidationError raised during (de)serialization.

  • data – The original input data.

  • many – Value of many on dump or load.

  • partial – Value of partial on load.

New in version 2.0.0.

Changed in version 3.0.0rc9: Receives many and partial (on deserialization) as keyword arguments.

load(data: Union[Mapping[str, Any], Iterable[Mapping[str, Any]]], *, many: Optional[bool] = None, partial: Optional[Union[bool, Sequence[str], Set[str]]] = None, unknown: Optional[str] = None)

Deserialize a data structure to an object defined by this Schema’s fields.

Parameters

  • data – The data to deserialize.

  • many – Whether to deserialize data as a collection. If None, the value for self.many is used.

  • partial – Whether to ignore missing fields and not require any fields declared. Propagates down to Nested fields as well. If its value is an iterable, only missing fields listed in that iterable will be ignored. Use dot delimiters to specify nested fields.

  • unknown – Whether to exclude, include, or raise an error for unknown fields in the data. Use EXCLUDE, INCLUDE or RAISE. If None, the value for self.unknown is used.

Returns

Deserialized data

New in version 1.0.0.

Changed in version 3.0.0b7: This method returns the deserialized data rather than a (data, errors) duple. A ValidationError is raised if invalid data are passed.

loads(json_data: str, *, many: Optional[bool] = None, partial: Optional[Union[bool, Sequence[str], Set[str]]] = None, unknown: Optional[str] = None, **kwargs)

Same as load(), except it takes a JSON string as input.

Parameters

  • json_data – A JSON string of the data to deserialize.

  • many – Whether to deserialize obj as a collection. If None, the value for self.many is used.

  • partial – Whether to ignore missing fields and not require any fields declared. Propagates down to Nested fields as well. If its value is an iterable, only missing fields listed in that iterable will be ignored. Use dot delimiters to specify nested fields.

  • unknown – Whether to exclude, include, or raise an error for unknown fields in the data. Use EXCLUDE, INCLUDE or RAISE. If None, the value for self.unknown is used.

Returns

Deserialized data

New in version 1.0.0.

Changed in version 3.0.0b7: This method returns the deserialized data rather than a (data, errors) duple. A ValidationError is raised if invalid data are passed.

on_bind_field(field_name: str, field_obj: marshmallow.fields.Field) → None

Hook to modify a field when it is bound to the Schema.

No-op by default.

validate(data: Mapping, *, many: Optional[bool] = None, partial: Optional[Union[bool, Sequence[str], Set[str]]] = None) → Dict[str, List[str]]

Validate data against the schema, returning a dictionary of validation errors.

Parameters

  • data – The data to validate.

  • many – Whether to validate data as a collection. If None, the value for self.many is used.

  • partial – Whether to ignore missing fields and not require any fields declared. Propagates down to Nested fields as well. If its value is an iterable, only missing fields listed in that iterable will be ignored. Use dot delimiters to specify nested fields.

Returns

A dictionary of validation errors.

New in version 1.1.0.

class labthings.Server(app, host='0.0.0.0', port=7485, debug=False, zeroconf=True)

Combined WSGI+mDNS server.

Parameters

  • host (string) – Host IP address. Defaults to 0.0.0.0.

  • port (int) – Host port. Defaults to 7485.

  • debug (bool) – Enable server debug mode. Defaults to False.

  • zeroconf (bool) – Enable the zeroconf (mDNS) server. Defaults to True.

run(host=None, port=None, debug=None, zeroconf=None)

Starts the server allowing for runtime parameters. Designed to immitate the old Flask app.run style of starting an app

Parameters

  • host (string) – Host IP address. Defaults to 0.0.0.0.

  • port (int) – Host port. Defaults to 7485.

  • debug (bool) – Enable server debug mode. Defaults to False.

  • zeroconf (bool) – Enable the zeroconf (mDNS) server. Defaults to True.

start()

Start the server and register mDNS records

class labthings.StrictLock(timeout: int = - 1, name: Optional[str] = None)

Class that behaves like a Python RLock, but with stricter timeout conditions and custom exceptions.

Parameters

timeout (int) – Time in seconds acquisition will wait before raising an exception

acquire(blocking: bool = True, timeout=<object object>, _strict: bool = True)
Parameters

  • blocking – (Default value = True)

  • timeout – (Default value = sentinel)

  • _strict – (Default value = True)

labthings.create_app(import_name, prefix: str = '', title: str = '', description: str = '', types: Optional[list] = None, version: str = '0.0.0', external_links: bool = True, handle_errors: bool = True, handle_cors: bool = True, flask_kwargs: Optional[dict] = None)

Quick-create a LabThings-enabled Flask app

Parameters

  • import_name – Flask import name. Usually __name__.

  • prefix (str) – URL prefix for all LabThings views. Defaults to “/api”.

  • title (str) – Title/name of the LabThings Thing.

  • description (str) – Brief description of the LabThings Thing.

  • version (str) – Version number/code of the Thing. Defaults to “0.0.0”.

  • handle_errors (bool) – Use the LabThings error handler, to JSON format internal exceptions. Defaults to True.

  • handle_cors (bool) – Automatically enable CORS on all LabThings views. Defaults to True.

  • flask_kwargs (dict) – Keyword arguments to pass to the Flask instance.

  • prefix – str: (Default value = “”)

  • title – str: (Default value = “”)

  • description – str: (Default value = “”)

  • types – list: (Default value = None)

  • version – str: (Default value = “0.0.0”)

  • external_links – bool: Use external links in Thing Description where possible

  • handle_errors – bool: (Default value = True)

  • handle_cors – bool: (Default value = True)

  • flask_kwargs – dict: (Default value = None)

Returns

(Flask app object, LabThings object)

labthings.current_action()

Return the ActionThread instance in which the caller is currently running.

If this function is called from outside an ActionThread, it will return None.

Returns

labthings.actions.ActionThread – Currently running ActionThread.

labthings.current_labthing(app=None)

The LabThing instance handling current requests.

Searches for a valid LabThing extension attached to the current Flask context.

Parameters

app – (Default value = None)

labthings.find_component(component_name: str, labthing_instance=None)

Find a particular LabThings Component registered to a LabThing instance

Parameters

  • component_name (str) – Fully qualified name of the component

  • labthing_instance (optional) – LabThing instance to search for the component. Defaults to current_labthing.

Returns

Python object registered as a component, or None if not found

labthings.find_extension(extension_name: str, labthing_instance=None)

Find a particular LabThings Extension registered to a LabThing instance

Parameters

  • extension_name (str) – Fully qualified name of the extension

  • labthing_instance (optional) – LabThing instance to search for the extension. Defaults to current_labthing.

Returns

LabThings Extension object, or None if not found

labthings.registered_components(labthing_instance=None)

Find all LabThings Components registered to a LabThing instance

Parameters

labthing_instance (optional) – LabThing instance to search for extensions. Defaults to current_labthing.

Returns

Python objects registered as LabThings components

Return type

list

labthings.registered_extensions(labthing_instance=None)

Find all LabThings Extensions registered to a LabThing instance

Parameters

labthing_instance (optional) – LabThing instance to search for extensions. Defaults to current_labthing.

Returns

LabThing Extension objects

Return type

list

labthings.update_action_data(data: dict)

Update the data of the ActionThread in which the caller is currently running.

If this function is called from outside an ActionThread, it will do nothing.

Parameters

data – dict: Action data dictionary

labthings.update_action_progress(progress: int)

Update the progress of the ActionThread in which the caller is currently running.

If this function is called from outside an ActionThread, it will do nothing.

Parameters

progress – int: Action progress, in percent (0-100)