# API


This page lists every public name with its signature, generated from the source. The guide explains what each one does.


## Core


`dd.asset` builds an asset from a schema, and `quarantine_spec` adds that asset's quarantine to the asset graph.


[asset()](asset.md#dagster_dataframely.asset)  
Turn the decorated function into an asset that validates the frame it returns against `schema`.

[quarantine_spec()](quarantine_spec.md#dagster_dataframely.quarantine_spec)  
Return an asset spec that adds an asset's quarantine to the asset graph.

[Granularity](Granularity.md#dagster_dataframely.Granularity)  
How many asset checks report a schema's rules: one per rule at `rule`, one per column with rules at `column`, and one for the schema at `schema`.

[SchemaRules](SchemaRules.md#dagster_dataframely.SchemaRules)  
Which checks report the schema-level rules at `column` granularity.


## Hand-wiring


`dd.asset` assembles these parts. Use them to build a `@dg.asset` yourself, where `dd.asset` does not fit.


[wiring.schema_metadata()](wiring.schema_metadata.md#dagster_dataframely.wiring.schema_metadata)  
Return the definition metadata that fills an asset's Columns tab from the schema.

[wiring.table_schema()](wiring.table_schema.md#dagster_dataframely.wiring.table_schema)  
Return the schema as the `dg.TableSchema` that Dagster's Columns tab shows.

[wiring.check_specs()](wiring.check_specs.md#dagster_dataframely.wiring.check_specs)  
Return the asset check specs for the schema's rules, plus the column-schema check.

[wiring.check_results()](wiring.check_results.md#dagster_dataframely.wiring.check_results)  
Yield a result for each check `check_specs` declares, without writing any rows.

[wiring.check_name()](wiring.check_name.md#dagster_dataframely.wiring.check_name)  
Return the asset check name for the Dataframely rule named `rule_name`.

[wiring.validation_results()](wiring.validation_results.md#dagster_dataframely.wiring.validation_results)  
Validate a frame and yield the asset's materialization and check results.

[wiring.AssetYield](wiring.AssetYield.md#dagster_dataframely.wiring.AssetYield)  
What `validation_results` yields: the asset's materialization, if the run writes its table, then one result per check. Use it as the return annotation of a hand-wired asset's function.

[wiring.QuarantineWriter](wiring.QuarantineWriter.md#dagster_dataframely.wiring.QuarantineWriter)  
A writer: a function that writes the invalid rows and returns the quarantine address, such as an asset key or a file path, as a string.

[wiring.delegating_writer()](wiring.delegating_writer.md#dagster_dataframely.wiring.delegating_writer)  
Return a writer that passes the invalid rows to the asset's own IO manager.

[wiring.file_writer()](wiring.file_writer.md#dagster_dataframely.wiring.file_writer)  
Return a writer that writes the invalid rows to a parquet file under `quarantine_dir`.

[wiring.quarantine_frame()](wiring.quarantine_frame.md#dagster_dataframely.wiring.quarantine_frame)  
Return the invalid rows as a writer receives them, with one rule column per rule.

[wiring.quarantine_path()](wiring.quarantine_path.md#dagster_dataframely.wiring.quarantine_path)  
Return the path of the parquet file `file_writer` writes an asset's invalid rows to.

[wiring.validate_quarantine_key()](wiring.validate_quarantine_key.md#dagster_dataframely.wiring.validate_quarantine_key)  
Raise if another asset already materializes the quarantine's asset key.


## Errors


This package raises these errors. Each one subclasses `DagsterDataframelyError`.


[errors.DagsterDataframelyError](errors.DagsterDataframelyError.md#dagster_dataframely.errors.DagsterDataframelyError)  
Base class for every error this package raises.

[errors.CollectionNotSupportedError](errors.CollectionNotSupportedError.md#dagster_dataframely.errors.CollectionNotSupportedError)  
`schema=` received a `dy.Collection`.

[errors.ReservedColumnError](errors.ReservedColumnError.md#dagster_dataframely.errors.ReservedColumnError)  
A column name is in the reserved `dy_` namespace.

[errors.InvalidColumnNameError](errors.InvalidColumnNameError.md#dagster_dataframely.errors.InvalidColumnNameError)  
A column name has a character Dagster does not allow in an asset check name.

[errors.CheckNameCollisionError](errors.CheckNameCollisionError.md#dagster_dataframely.errors.CheckNameCollisionError)  
Two rules produce the same asset check name.

[errors.InvalidSettingError](errors.InvalidSettingError.md#dagster_dataframely.errors.InvalidSettingError)  
A setting has a value it does not allow.

[errors.MaterializeResultValueError](errors.MaterializeResultValueError.md#dagster_dataframely.errors.MaterializeResultValueError)  
A returned `dg.MaterializeResult` has no frame in `value`.

[errors.MaterializeResultFieldError](errors.MaterializeResultFieldError.md#dagster_dataframely.errors.MaterializeResultFieldError)  
A returned `dg.MaterializeResult` sets `asset_key` or `check_results`.

[errors.ColumnSchemaError](errors.ColumnSchemaError.md#dagster_dataframely.errors.ColumnSchemaError)  
A frame's columns or dtypes do not match the schema.

[errors.ValidationAbortError](errors.ValidationAbortError.md#dagster_dataframely.errors.ValidationAbortError)  
Rows failed validation and the asset declares no quarantine, so it writes nothing.

[errors.NoValidRowsError](errors.NoValidRowsError.md#dagster_dataframely.errors.NoValidRowsError)  
Every row failed validation, so the run wrote only the quarantine.

[errors.QuarantineKeyCollisionError](errors.QuarantineKeyCollisionError.md#dagster_dataframely.errors.QuarantineKeyCollisionError)  
Another asset already materializes the quarantine's asset key.

[errors.QuarantineDirError](errors.QuarantineDirError.md#dagster_dataframely.errors.QuarantineDirError)  
Invalid rows need writing, and nothing sets `quarantine_dir`.