Flyte and Python Types

FlyteKit automatically maps Python types to Flyte types. This section provides details of the mappings, but for the most part you can skip this section, as almost all of Python types are mapped automatically.

The following table provides a quick overview of how types are converted from the type-hints (python native) to Flyte-understood, cross-language types.

Supported Python types and mapping to underlying Flyte Type

Python Type	Flyte Type	Conversion	Comment
int	Integer	Automatic	just use python 3 type hints
float	Float	Automatic	just use python 3 type hints
str	String	Automatic	just use python 3 type hints
bool	Boolean	Automatic	just use python 3 type hints
bytes/bytearray	binary	Not Supported	Let us know if this is an interesting usecase that you can currently support using your own transformers.
complex	NA	Not Supported	Let us know if this is an interesting usecase that you can currently support using your own transformers.
datetime.timedelta	Duration	Automatic	just use python 3 type hints
datetime.datetime	Datetime	Automatic	just use python 3 type hints
Univariate List / typing.List	Collection [ type ]	Automatic	Use python 3 type hints e.g typing.List[T], where T can be one of the other supported types in the table
file / file-like / os.PathLike / flytekit.types.file.FlyteFile	Blob - Single	Automatic	Use python 3 type hints. if using file / os.PathLike objects then, Flyte will default to binary protocol for the file. If using FlyteFile[“protocol”], it is assumed that the file is in the specified protocol. e.g. “jpg”, “png”, “hdf5” etc
Directory / flytekit.types.directory.FlyteDirectory	Blob - MultiPart	Automatic	Use python 3 type hints. If using FlyteDirectory[“protocol”] it is assumed that all the files are of the specified protocol
Typed dictionary with str key - typing.Dict[str, V]	Map[str, V]	Automatic	Use python 3 type hints e.g typing.Dict[str, V], where V can be one of the other supported types in the table even another Dictionary (nested)
Untyped dictionary - dict	JSON (struct.pb)	Automatic	Use python 3 type hints e.g dict, it will be assumed that we can convert the dict to json. This may not always be possible and will cause a RuntimeError
Dataclasses @dataclass	Struct	Automatic	Use python 3 type hints. The class should be a pure value class and should be annotated with @dataclass and @dataclass_json.
pandas.DataFrame	Schema	Automatic	Use python 3 type hints. Pandas column types are not preserved
pyspark.DataFrame	Schema	Automatic	Use python 3 type hints. Column types are not preserved. Install flytekitplugins-spark plugin using pip
FlyteSchema[Columns, format]	Schema	Automatic	Use python 3 type hints. Column types are not preserved
User defined types	Any	Custom Transformers	Use python 3 type hints. We use FlytePickle transformer by default, but users still can provide custom transformers. Refer to Writing Custom Flyte Types.