`prefect.exceptions`

Prefect-specific exceptions.

Functions

`exception_traceback`

exception_traceback(exc: Exception) -> str

Convert an exception to a printable string with a traceback

Classes

`PrefectException`

Base exception type for Prefect errors.

`CrashedRun`

Raised when the result from a crashed run is retrieved. This occurs when a string is attached to the state instead of an exception or if the state’s data is null.

`FailedRun`

Raised when the result from a failed run is retrieved and an exception is not attached. This occurs when a string is attached to the state instead of an exception or if the state’s data is null.

`CancelledRun`

Raised when the result from a cancelled run is retrieved and an exception is not attached. This occurs when a string is attached to the state instead of an exception or if the state’s data is null.

`PausedRun`

Raised when the result from a paused run is retrieved.

`UnfinishedRun`

Raised when the result from a run that is not finished is retrieved. For example, if a run is in a SCHEDULED, PENDING, CANCELLING, or RUNNING state.

`MissingFlowError`

Raised when a given flow name is not found in the expected script.

`UnspecifiedFlowError`

Raised when multiple flows are found in the expected script and no name is given.

`MissingResult`

Raised when a result is missing from a state; often when result persistence is disabled and the state is retrieved from the API.

`ScriptError`

Raised when a script errors during evaluation while attempting to load data

`ParameterTypeError`

Raised when a parameter does not pass Pydantic type validation. Methods:

`from_validation_error`

from_validation_error(cls, exc: ValidationError) -> Self

`ParameterBindError`

Raised when args and kwargs cannot be converted to parameters. Methods:

`from_bind_failure`

from_bind_failure(cls, fn: Callable[..., Any], exc: TypeError, call_args: tuple[Any, ...], call_kwargs: dict[str, Any]) -> Self

`SignatureMismatchError`

Raised when parameters passed to a function do not match its signature. Methods:

`from_bad_params`

from_bad_params(cls, expected_params: list[str], provided_params: list[str]) -> Self

`ObjectNotFound`

Raised when the client receives a 404 (not found) from the API.

`ObjectAlreadyExists`

Raised when the client receives a 409 (conflict) from the API.

`ObjectLimitReached`

Raised when the client receives a 403 (forbidden) from the API due to reaching an object limit (e.g. maximum number of deployments).

`ObjectUnsupported`

Raised when the client receives a 403 (forbidden) from the API due to an unsupported object (i.e. requires a specific Prefect Cloud tier).

`UpstreamTaskError`

Raised when a task relies on the result of another task but that task is not ‘COMPLETE’

`MissingContextError`

Raised when a method is called that requires a task or flow run context to be active but one cannot be found.

`MissingProfileError`

Raised when a profile name does not exist.

`ReservedArgumentError`

Raised when a function used with Prefect has an argument with a name that is reserved for a Prefect feature

`InvalidNameError`

Raised when a name contains characters that are not permitted.

`PrefectSignal`

Base type for signal-like exceptions that should never be caught by users.

`Abort`

Raised when the API sends an ‘ABORT’ instruction during state proposal. Indicates that the run should exit immediately.

`Pause`

Raised when a flow run is PAUSED and needs to exit for resubmission.

`ExternalSignal`

Base type for external signal-like exceptions that should never be caught by users.

`TerminationSignal`

Raised when a flow run receives a termination signal.

`PrefectHTTPStatusError`

Raised when client receives a Response that contains an HTTPStatusError. Used to include API error details in the error messages that the client provides users. Methods:

`from_httpx_error`

from_httpx_error(cls: type[Self], httpx_error: HTTPStatusError) -> Self

Generate a PrefectHTTPStatusError from an httpx.HTTPStatusError.

`MappingLengthMismatch`

Raised when attempting to call Task.map with arguments of different lengths.

`MappingMissingIterable`

Raised when attempting to call Task.map with all static arguments

`BlockMissingCapabilities`

Raised when a block does not have required capabilities for a given operation.

`ProtectedBlockError`

Raised when an operation is prevented due to block protection.

`InvalidRepositoryURLError`

Raised when an incorrect URL is provided to a GitHub filesystem block.

`InfrastructureError`

A base class for exceptions related to infrastructure blocks

`InfrastructureNotFound`

Raised when infrastructure is missing, likely because it has exited or been deleted.

`InfrastructureNotAvailable`

Raised when infrastructure is not accessible from the current machine. For example, if a process was spawned on another machine it cannot be managed.

`NotPausedError`

Raised when attempting to unpause a run that isn’t paused.

`FlowPauseTimeout`

Raised when a flow pause times out

`FlowRunWaitTimeout`

Raised when a flow run takes longer than a given timeout

`PrefectImportError`

An error raised when a Prefect object cannot be imported due to a move or removal.

`SerializationError`

Raised when an object cannot be serialized.

`ConfigurationError`

Raised when a configuration is invalid.

`ProfileSettingsValidationError`

Raised when a profile settings are invalid.

`HashError`

Raised when hashing objects fails

API Reference

​prefect.exceptions

​Functions

​exception_traceback

​Classes

​PrefectException

​CrashedRun

​FailedRun

​CancelledRun

​PausedRun

​UnfinishedRun

​MissingFlowError

​UnspecifiedFlowError

​MissingResult

​ScriptError

​ParameterTypeError

​from_validation_error

​ParameterBindError

​from_bind_failure

​SignatureMismatchError

​from_bad_params

​ObjectNotFound

​ObjectAlreadyExists

​ObjectLimitReached

​ObjectUnsupported

​UpstreamTaskError

​MissingContextError

​MissingProfileError

​ReservedArgumentError

​InvalidNameError

​PrefectSignal

​Abort

​Pause

​ExternalSignal

​TerminationSignal

​PrefectHTTPStatusError

​from_httpx_error

​MappingLengthMismatch

​MappingMissingIterable

​BlockMissingCapabilities

​ProtectedBlockError

​InvalidRepositoryURLError

​InfrastructureError

​InfrastructureNotFound

​InfrastructureNotAvailable

​NotPausedError

​FlowPauseTimeout

​FlowRunWaitTimeout

​PrefectImportError

​SerializationError

​ConfigurationError

​ProfileSettingsValidationError

​HashError