ToArrow#

class lsst.daf.butler.arrow_utils.ToArrow#

Bases: ABC

An abstract interface for converting objects to an Arrow field of the appropriate type.

Attributes Summary

`data_type`	Arrow data type for the field this converter produces.
`field`	Arrow field this converter produces.
`name`	Name of the field.
`nullable`	Whether the field permits null or `None` values.

Methods Summary

`append`(value, column)	Append an object's arrow representation to a `list`.
`dictionary_encoded`()	Return a new converter with the same name and type, but using dictionary encoding (to 32-bit integers) to compress duplicate values.
`finish`(column)	Convert a list of values constructed via `append` into an Arrow array.
`for_datetime`(name[, nullable])	Return a converter for `astropy.time.Time`, stored as TAI nanoseconds since 1970-01-01.
`for_primitive`(name, data_type, nullable)	Return a converter for a primitive type already supported by Arrow.
`for_region`(name[, nullable])	Return a converter for `lsst.sphgeom.Region`.
`for_timespan`(name[, nullable])	Return a converter for `lsst.daf.butler.Timespan`.
`for_uuid`(name[, nullable])	Return a converter for `uuid.UUID`.

Attributes Documentation

data_type#: Arrow data type for the field this converter produces.

field#: Arrow field this converter produces.

name#: Name of the field.

nullable#: Whether the field permits null or None values.

Methods Documentation

abstract append(value: Any, column: list[Any]) → None#

Append an object’s arrow representation to a list.

Parameters#

valueobject: Original value to be converted to a row in an Arrow column.
columnlist: List of values to append to. The type of value to append is implementation-defined; the only requirement is that finish be able to handle this list later.

dictionary_encoded() → ToArrow#: Return a new converter with the same name and type, but using dictionary encoding (to 32-bit integers) to compress duplicate values.

abstract finish(column: list[Any]) → Array#

Convert a list of values constructed via append into an Arrow array.

Parameters#

columnlist: List of column values populated by append.

static for_datetime(name: str, nullable: bool = True) → ToArrow#

Return a converter for astropy.time.Time, stored as TAI nanoseconds since 1970-01-01.

Parameters#

namestr: Name of the schema field.
nullablebool: Whether the field should permit null or None values.

Returns#

to_arrowToArrow: Converter instance.

static for_primitive(name: str, data_type: DataType, nullable: bool) → ToArrow#

Return a converter for a primitive type already supported by Arrow.

Parameters#

namestr: Name of the schema field.
data_typepyarrow.DataType: Arrow data type object.
nullablebool: Whether the field should permit null or None values.

Returns#

to_arrowToArrow: Converter instance.

static for_region(name: str, nullable: bool = True) → ToArrow#

Return a converter for lsst.sphgeom.Region.

Parameters#

namestr: Name of the schema field.
nullablebool: Whether the field should permit null or None values.

Returns#

to_arrowToArrow: Converter instance.

static for_timespan(name: str, nullable: bool = True) → ToArrow#

Return a converter for lsst.daf.butler.Timespan.

Parameters#

namestr: Name of the schema field.
nullablebool: Whether the field should permit null or None values.

Returns#

to_arrowToArrow: Converter instance.

static for_uuid(name: str, nullable: bool = True) → ToArrow#

Return a converter for uuid.UUID.

Parameters#

namestr: Name of the schema field.
nullablebool: Whether the field should permit null or None values.

Returns#

to_arrowToArrow: Converter instance.