labthings_fastapi.exceptions

A submodule for custom LabThings-FastAPI Exceptions.

Exceptions

NotConnectedToServerError	The Thing is not connected to a server.
ServerNotRunningError	The ThingServer is not running.
ReadOnlyPropertyError	A property is read-only.
PropertyNotObservableError	The property is not observable.
InconsistentTypeError	Different type hints have been given for a descriptor.
MissingTypeError	No type hints have been given for a descriptor that requires a type.
ThingNotConnectedError	ThingSlots have not yet been set up.
ThingSlotError	A ThingSlot could not be set up.
InvocationCancelledError	An invocation was cancelled by the user.
InvocationError	The invocation ended in an anticipated error state.
NoInvocationContextError	An invocation-specific resource has been requested from outside an invocation.
LogConfigurationError	There is a problem with logging configuration.
NoBlobManagerError	Raised if an API route accesses Invocation outputs without a BlobIOContextDep.
NoUrlForContextError	Raised if URLFor is serialised without a url_for context variable being set.
UnsupportedConstraintError	A constraint argument is not supported.
FailedToInvokeActionError	The action could not be started.
ServerActionError	The action ended with an error on the server.
ClientPropertyError	Setting or getting a property via a ThingClient failed.
NotBoundToInstanceError	A BaseDescriptorInfo is not bound to an object.

Module Contents

exception labthings_fastapi.exceptions.NotConnectedToServerError

Bases: RuntimeError

The Thing is not connected to a server.

This exception is called if an Action is called or a DataProperty is updated on a Thing that is not connected to a ThingServer.

A server connection is needed to manage asynchronous behaviour.

Thing instances are also only assigned a path when they are added to a server, so this error may be raised by functions that implement the HTTP API if an attempt is made to construct the API before the Thing has been assigned a path.

Initialize self. See help(type(self)) for accurate signature.

exception labthings_fastapi.exceptions.ServerNotRunningError

Bases: RuntimeError

The ThingServer is not running.

This exception is called when a function assumes the ThingServer is running, and it is not. This might be because the function needs to call code in the async event loop.

Initialize self. See help(type(self)) for accurate signature.

exception labthings_fastapi.exceptions.ReadOnlyPropertyError

Bases: AttributeError

A property is read-only.

No setter has been defined for this FunctionalProperty, so it may not be written to.

Initialize self. See help(type(self)) for accurate signature.

exception labthings_fastapi.exceptions.PropertyNotObservableError

Bases: RuntimeError

The property is not observable.

This exception is raised when Thing.observe_property is called with a property that is not observable. Currently, only data properties are observable: functional properties (using a getter/setter) may not be observed.

Initialize self. See help(type(self)) for accurate signature.

exception labthings_fastapi.exceptions.InconsistentTypeError

Bases: TypeError

Different type hints have been given for a descriptor.

Some descriptors in LabThings, particularly DataProperty and ThingSlot may have their type specified in different ways. If multiple type hints are provided, they must match. See property for more details.

Initialize self. See help(type(self)) for accurate signature.

exception labthings_fastapi.exceptions.MissingTypeError

Bases: TypeError

No type hints have been given for a descriptor that requires a type.

Every property and thing connection should have a type hint, There are different ways of providing these type hints. This error indicates that no type hint was found.

See documentation for property and thing_slot for more details.

Initialize self. See help(type(self)) for accurate signature.

exception labthings_fastapi.exceptions.ThingNotConnectedError

Bases: RuntimeError

ThingSlots have not yet been set up.

This error is raised if a ThingSlot is accessed before the Thing has been supplied by the LabThings server. This usually happens because either the Thing is being used without a server (in which case the attribute should be mocked), or because it has been accessed before __enter__ has been called.

Initialize self. See help(type(self)) for accurate signature.

exception labthings_fastapi.exceptions.ThingSlotError

Bases: RuntimeError

A ThingSlot could not be set up.

This error is raised if the LabThings server is unable to set up a ThingSlot, for example because the named Thing does not exist, or is of the wrong type, or is not specified and there is no default.

Initialize self. See help(type(self)) for accurate signature.

exception labthings_fastapi.exceptions.InvocationCancelledError

Bases: BaseException

An invocation was cancelled by the user.

Note that this inherits from BaseException so won’t be caught by except Exception, it must be handled specifically.

Action code may want to handle cancellation gracefully. This exception should be propagated if the action’s status should be reported as cancelled, or it may be handled so that the action finishes, returns a value, and is marked as completed.

If this exception is handled and not re-raised, or if it arises in a manually-created thread, the action will continue as normal. It is a good idea to make sure your action terminates soon after this exception is raised.

Initialize self. See help(type(self)) for accurate signature.

exception labthings_fastapi.exceptions.InvocationError

Bases: RuntimeError

The invocation ended in an anticipated error state.

When this error is raised, action execution stops as expected. The exception will be logged at error level without a traceback, and the invocation will return with error status.

Subclass this error for errors that do not need further traceback information to be provided with the error message in logs.

Initialize self. See help(type(self)) for accurate signature.

exception labthings_fastapi.exceptions.NoInvocationContextError

Bases: RuntimeError

An invocation-specific resource has been requested from outside an invocation.

This error is raised when the current invocation ID is requested, and there is no current invocation ID. Invocation ID is determined from context (using a ContextVar ) and is available from within action functions.

To avoid this error in test code or manually created threads, you should supply an invocation context.

Initialize self. See help(type(self)) for accurate signature.

exception labthings_fastapi.exceptions.LogConfigurationError

Bases: RuntimeError

There is a problem with logging configuration.

LabThings uses the logging module to collect logs from actions. This requires certain handlers and filters to be set up. This exception is raised if they cannot be added, or if they are not present when they are needed.

Initialize self. See help(type(self)) for accurate signature.

exception labthings_fastapi.exceptions.NoBlobManagerError

Bases: RuntimeError

Raised if an API route accesses Invocation outputs without a BlobIOContextDep.

Any access to an invocation output must have BlobIOContextDep as a dependency, as the output may be a blob, and the blob needs this context to resolve its URL.

Initialize self. See help(type(self)) for accurate signature.

exception labthings_fastapi.exceptions.NoUrlForContextError

Bases: RuntimeError

Raised if URLFor is serialised without a url_for context variable being set.

This usually indicates that URLFor is being serialised somewhere other than in an HTTP response, for example in test code or in a background task. In these cases, you should set up the url_for context variable manually, for example using the testing.use_dummy_url_for context manager.

Initialize self. See help(type(self)) for accurate signature.

exception labthings_fastapi.exceptions.UnsupportedConstraintError

Bases: ValueError

A constraint argument is not supported.

This exception is raised when a constraint argument is passed to a property that is not in the supported list. See labthings_fastapi.properties.CONSTRAINT_ARGS for the list of supported arguments. Their meaning is described in the pydantic.Field documentation.

Initialize self. See help(type(self)) for accurate signature.

exception labthings_fastapi.exceptions.FailedToInvokeActionError

Bases: RuntimeError

The action could not be started.

This error is raised by a ThingClient instance if an action could not be started. It most commonly occurs because the input to the action could not be converted to the required type: the error message should give more detail on what’s wrong.

Initialize self. See help(type(self)) for accurate signature.

exception labthings_fastapi.exceptions.ServerActionError

Bases: RuntimeError

The action ended with an error on the server.

This error is raised by a ThingClient when an action is successfully invoked on the server, but does not complete. The error message should include more information on why this happened.

Initialize self. See help(type(self)) for accurate signature.

exception labthings_fastapi.exceptions.ClientPropertyError

Bases: RuntimeError

Setting or getting a property via a ThingClient failed.

Initialize self. See help(type(self)) for accurate signature.

exception labthings_fastapi.exceptions.NotBoundToInstanceError

Bases: RuntimeError

A BaseDescriptorInfo is not bound to an object.

Some methods and properties of BaseDescriptorInfo objects require them to be bound to a Thing instance. If these methods are called on a BaseDescriptorInfo object that is unbound, this exception is raised.

This exception should only be seen when BaseDescriptorInfo objects are generated from a Thing class. Usually, they should be accessed via a Thing instance, in which case they will be bound.

Initialize self. See help(type(self)) for accurate signature.