_mapping - Chirp

data._mapping

module

Row-to-dataclass mapping with type coercion.

Converts raw database rows (tuples or dicts) into typed frozen dataclasses. Uses dataclass field introspection — no metaclass magic, no descriptors.

Type coercion handles the mismatch between…

Row-to-dataclass mapping with type coercion.

Converts raw database rows (tuples or dicts) into typed frozen dataclasses. Uses dataclass field introspection — no metaclass magic, no descriptors.

Type coercion handles the mismatch between database drivers (SQLite returns strings for some column types) and Python dataclass annotations. Fields annotated asint will coerce string values like "45" to 45, and empty strings to0.

data._mapping

Name	Type	Default	Description
`type`		—
`qualified_name`		—
`element_type`		—
`description`		—
`source_file`		—
`line_number`		—
`is_autodoc`		—
`autodoc_element`		—
`_autodoc_template`		—
`_autodoc_url_path`		—
`_autodoc_page_type`		—
`title`		—
`doc_content_hash`		—

Symbols on this page

function _build_coercion_map

Build a {field_name: target_type} map for coercible fields.

ReturnsNonefor fields that don't need coercion (complex types, generics, etc.).

function _coerce

Coerce a single value to the target type, if needed.

function map_row

Map a dict-like row to a frozen dataclass instance.

Only passes keys that match dataclass fields. Extra columns are silently ignored (SELECT * is…

function map_rows

Map a list of dict-like rows to frozen dataclass instances.

_build_coercion_map

function

def _build_coercion_map(cls: type) -> dict[str, type | None]

Build a {field_name: target_type} map for coercible fields.

ReturnsNonefor fields that don't need coercion (complex types, generics, etc.).

Parameters

Name	Type	Default	Description
`cls`	`type`	—

_coerce

function

def _coerce(value: Any, target: type | None) -> Any

Coerce a single value to the target type, if needed.

Parameters

Name	Type	Default	Description
`value`	`Any`	—
`target`	`type \| None`	—

map_row

function

def map_row(cls: type[T], row: dict[str, Any]) -> T

Map a dict-like row to a frozen dataclass instance.

Only passes keys that match dataclass fields. Extra columns are silently ignored (SELECT * is fine even if the dataclass has fewer fields).

Values are coerced to match field annotations:int, float, bool, and strfields handle driver type mismatches automatically. Empty strings inint/float columns coerce to 0/0.0.

RaisesTypeErrorif required fields are missing from the row.

Parameters

Name	Type	Default	Description
`cls`	`type[T]`	—
`row`	`dict[str, Any]`	—

map_rows

function

def map_rows(cls: type[T], rows: list[dict[str, Any]]) -> list[T]

Map a list of dict-like rows to frozen dataclass instances.

Parameters

Name	Type	Default	Description
`cls`	`type[T]`	—
`rows`	`list[dict[str, Any]]`	—

View source · /home/runner/work/chirp/chirp/site/../src/chirp/data/_mapping.py:1