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prefect.blocks.core

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Functions

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block_schema_to_key 

block_schema_to_key(schema: BlockSchema) -> str
Defines the unique key used to lookup the Block class for a given schema.

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schema_extra 

schema_extra(schema: dict[str, Any], model: type['Block']) -> None
Customizes Pydantic’s schema generation feature to add blocks related information.

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Classes

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InvalidBlockRegistration

Raised on attempted registration of the base Block class or a Block interface class

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UnknownBlockType

Raised when a block type is not found in the registry.

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BlockNotSavedError

Raised when a given block is not saved and an operation that requires the block to be saved is attempted.

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Block

A base class for implementing a block that wraps an external service. This class can be defined with an arbitrary set of fields and methods, and couples business logic with data contained in an block document. _block_document_name, _block_document_id, _block_schema_id, and _block_type_id are reserved by Prefect as Block metadata fields, but otherwise a Block can implement arbitrary logic. Blocks can be instantiated without populating these metadata fields, but can only be used interactively, not with the Prefect API. Instead of the init method, a block implementation allows the definition of a block_initialization method that is called after initialization. Methods:

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aload 

aload(cls, name: str, validate: bool = True, client: Optional['PrefectClient'] = None) -> 'Self'
Retrieves data from the block document with the given name for the block type that corresponds with the current class and returns an instantiated version of the current class with the data stored in the block document. If a block document for a given block type is saved with a different schema than the current class calling aload, a warning will be raised. If the current class schema is a subset of the block document schema, the block can be loaded as normal using the default validate = True. If the current class schema is a superset of the block document schema, aload must be called with validate set to False to prevent a validation error. In this case, the block attributes will default to None and must be set manually and saved to a new block document before the block can be used as expected. Args:
  • name: The name or slug of the block document. A block document slug is a string with the format <block_type_slug>/<block_document_name>
  • validate: If False, the block document will be loaded without Pydantic validating the block schema. This is useful if the block schema has changed client-side since the block document referred to by name was saved.
  • client: The client to use to load the block document. If not provided, the default client will be injected.
Raises:
  • ValueError: If the requested block document is not found.
Returns:
  • An instance of the current class hydrated with the data stored in the
  • block document with the specified name.
Examples: Load from a Block subclass with a block document name: 
class Custom(Block):
    message: str

Custom(message="Hello!").save("my-custom-message")

loaded_block = await Custom.aload("my-custom-message")
Load from Block with a block document slug: 
class Custom(Block):
    message: str

Custom(message="Hello!").save("my-custom-message")

loaded_block = await Block.aload("custom/my-custom-message")
Migrate a block document to a new schema: 
# original class
class Custom(Block):
    message: str

Custom(message="Hello!").save("my-custom-message")

# Updated class with new required field
class Custom(Block):
    message: str
    number_of_ducks: int

loaded_block = await Custom.aload("my-custom-message", validate=False)

# Prints UserWarning about schema mismatch

loaded_block.number_of_ducks = 42

loaded_block.save("my-custom-message", overwrite=True)

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annotation_refers_to_block_class 

annotation_refers_to_block_class(annotation: Any) -> bool

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block_initialization 

block_initialization(self) -> None

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delete 

delete(cls, name: str, client: Optional['PrefectClient'] = None)

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get_block_capabilities 

get_block_capabilities(cls) -> FrozenSet[str]
Returns the block capabilities for this Block. Recursively collects all block capabilities of all parent classes into a single frozenset.

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get_block_class_from_key 

get_block_class_from_key(cls: type[Self], key: str) -> type[Self]
Retrieve the block class implementation given a key.

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get_block_class_from_schema 

get_block_class_from_schema(cls: type[Self], schema: BlockSchema) -> type[Self]
Retrieve the block class implementation given a schema.

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get_block_placeholder 

get_block_placeholder(self) -> str
Returns the block placeholder for the current block which can be used for templating. Returns:
  • The block placeholder for the current block in the format prefect.blocks.{block_type_name}.{block_document_name}
Raises:
  • BlockNotSavedError: Raised if the block has not been saved.
If a block has not been saved, the return value will be None.

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get_block_schema_version 

get_block_schema_version(cls) -> str

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get_block_type_name 

get_block_type_name(cls) -> str

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get_block_type_slug 

get_block_type_slug(cls) -> str

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get_code_example 

get_code_example(cls) -> Optional[str]
Returns the code example for the given block. Attempts to parse code example from the class docstring if an override is not provided.

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get_description 

get_description(cls) -> Optional[str]
Returns the description for the current block. Attempts to parse description from class docstring if an override is not defined.

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is_block_class 

is_block_class(block: Any) -> TypeGuard[type['Block']]

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load 

load(cls, name: str, validate: bool = True, client: Optional['PrefectClient'] = None) -> 'Self'
Retrieves data from the block document with the given name for the block type that corresponds with the current class and returns an instantiated version of the current class with the data stored in the block document. If a block document for a given block type is saved with a different schema than the current class calling load, a warning will be raised. If the current class schema is a subset of the block document schema, the block can be loaded as normal using the default validate = True. If the current class schema is a superset of the block document schema, load must be called with validate set to False to prevent a validation error. In this case, the block attributes will default to None and must be set manually and saved to a new block document before the block can be used as expected. Args:
  • name: The name or slug of the block document. A block document slug is a string with the format <block_type_slug>/<block_document_name>
  • validate: If False, the block document will be loaded without Pydantic validating the block schema. This is useful if the block schema has changed client-side since the block document referred to by name was saved.
  • client: The client to use to load the block document. If not provided, the default client will be injected.
Raises:
  • ValueError: If the requested block document is not found.
Returns:
  • An instance of the current class hydrated with the data stored in the
  • block document with the specified name.
Examples: Load from a Block subclass with a block document name: 
class Custom(Block):
    message: str

Custom(message="Hello!").save("my-custom-message")

loaded_block = Custom.load("my-custom-message")
Load from Block with a block document slug: 
class Custom(Block):
    message: str

Custom(message="Hello!").save("my-custom-message")

loaded_block = Block.load("custom/my-custom-message")
Migrate a block document to a new schema: 
# original class
class Custom(Block):
    message: str

Custom(message="Hello!").save("my-custom-message")

# Updated class with new required field
class Custom(Block):
    message: str
    number_of_ducks: int

loaded_block = Custom.load("my-custom-message", validate=False)

# Prints UserWarning about schema mismatch

loaded_block.number_of_ducks = 42

loaded_block.save("my-custom-message", overwrite=True)

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load_from_ref 

load_from_ref(cls, ref: Union[str, UUID, dict[str, Any]], validate: bool = True, client: 'PrefectClient | None' = None) -> Self
Retrieves data from the block document by given reference for the block type that corresponds with the current class and returns an instantiated version of the current class with the data stored in the block document. Provided reference can be a block document ID, or a reference data in dictionary format. Supported dictionary reference formats are:
  • {"block_document_id": <block_document_id>}
  • {"block_document_slug": <block_document_slug>}
If a block document for a given block type is saved with a different schema than the current class calling load, a warning will be raised. If the current class schema is a subset of the block document schema, the block can be loaded as normal using the default validate = True. If the current class schema is a superset of the block document schema, load must be called with validate set to False to prevent a validation error. In this case, the block attributes will default to None and must be set manually and saved to a new block document before the block can be used as expected. Args:
  • ref: The reference to the block document. This can be a block document ID, or one of supported dictionary reference formats.
  • validate: If False, the block document will be loaded without Pydantic validating the block schema. This is useful if the block schema has changed client-side since the block document referred to by name was saved.
  • client: The client to use to load the block document. If not provided, the default client will be injected.
Raises:
  • ValueError: If invalid reference format is provided.
  • ValueError: If the requested block document is not found.
Returns:
  • An instance of the current class hydrated with the data stored in the
  • block document with the specified name.

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model_dump 

model_dump(self) -> dict[str, Any]

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model_json_schema 

model_json_schema(cls, by_alias: bool = True, ref_template: str = '#/definitions/{model}', schema_generator: type[GenerateJsonSchema] = GenerateJsonSchema, mode: Literal['validation', 'serialization'] = 'validation') -> dict[str, Any]
TODO: stop overriding this method - use GenerateSchema in ConfigDict instead?

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model_validate 

model_validate(cls: type[Self], obj: dict[str, Any] | Any) -> Self

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register_type_and_schema 

register_type_and_schema(cls, client: Optional['PrefectClient'] = None)
Makes block available for configuration with current Prefect API. Recursively registers all nested blocks. Registration is idempotent. Args:
  • client: Optional client to use for registering type and schema with the Prefect API. A new client will be created and used if one is not provided.

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save 

save(self, name: Optional[str] = None, overwrite: bool = False, client: Optional['PrefectClient'] = None)
Saves the values of a block as a block document. Args:
  • name: User specified name to give saved block document which can later be used to load the block document.
  • overwrite: Boolean value specifying if values should be overwritten if a block document with the specified name already exists.

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ser_model 

ser_model(self, handler: SerializerFunctionWrapHandler, info: SerializationInfo) -> Any

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validate_block_type_slug 

validate_block_type_slug(cls, values: Any) -> Any
Validates that the block_type_slug in the input values matches the expected block type slug for the class. This helps pydantic to correctly discriminate between different Block subclasses when validating Union types of Blocks.
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