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prefect.exceptions

Prefect-specific exceptions.

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Functions

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exception_traceback ^↗

exception_traceback(exc: Exception) -> str

Convert an exception to a printable string with a traceback

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Classes

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PrefectException ^↗

Base exception type for Prefect errors.

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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.

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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.

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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.

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PausedRun ^↗

Raised when the result from a paused run is retrieved.

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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.

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MissingFlowError ^↗

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

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UnspecifiedFlowError ^↗

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

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MissingResult ^↗

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

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ScriptError ^↗

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

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ParameterTypeError ^↗

Raised when a parameter does not pass Pydantic type validation.

Methods:

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from_validation_error ^↗

from_validation_error(cls, exc: ValidationError) -> Self

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ParameterBindError ^↗

Raised when args and kwargs cannot be converted to parameters.

Methods:

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from_bind_failure ^↗

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

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SignatureMismatchError ^↗

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

Methods:

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from_bad_params ^↗

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

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ObjectNotFound ^↗

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

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ObjectAlreadyExists ^↗

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

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UpstreamTaskError ^↗

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

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MissingContextError ^↗

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

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MissingProfileError ^↗

Raised when a profile name does not exist.

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ReservedArgumentError ^↗

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

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InvalidNameError ^↗

Raised when a name contains characters that are not permitted.

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PrefectSignal ^↗

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

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Abort ^↗

Raised when the API sends an ‘ABORT’ instruction during state proposal.

Indicates that the run should exit immediately.

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Pause ^↗

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

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ExternalSignal ^↗

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

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TerminationSignal ^↗

Raised when a flow run receives a termination signal.

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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:

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from_httpx_error ^↗

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

Generate a PrefectHTTPStatusError from an httpx.HTTPStatusError.

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MappingLengthMismatch ^↗

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

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MappingMissingIterable ^↗

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

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BlockMissingCapabilities ^↗

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

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ProtectedBlockError ^↗

Raised when an operation is prevented due to block protection.

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InvalidRepositoryURLError ^↗

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

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InfrastructureError ^↗

A base class for exceptions related to infrastructure blocks

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InfrastructureNotFound ^↗

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

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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.

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NotPausedError ^↗

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

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FlowPauseTimeout ^↗

Raised when a flow pause times out

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FlowRunWaitTimeout ^↗

Raised when a flow run takes longer than a given timeout

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PrefectImportError ^↗

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

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SerializationError ^↗

Raised when an object cannot be serialized.

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ConfigurationError ^↗

Raised when a configuration is invalid.

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ProfileSettingsValidationError ^↗

Raised when a profile settings are invalid.

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HashError ^↗

Raised when hashing objects fails