"""``EagerPolarsDataset`` loads/saves data from/to a data file using an underlying
filesystem (e.g.: local, S3, GCS). It uses polars to handle the
type of read/write target.
"""
from __future__ import annotations
from copy import deepcopy
from io import BytesIO
from pathlib import PurePosixPath
from typing import Any
import fsspec
import polars as pl
from kedro.io.core import (
AbstractVersionedDataset,
DatasetError,
Version,
get_filepath_str,
get_protocol_and_path,
)
[docs]
class EagerPolarsDataset(AbstractVersionedDataset[pl.DataFrame, pl.DataFrame]):
"""``polars.EagerPolarsDataset`` loads/saves data from/to a data file using an underlying
filesystem (e.g.: local, S3, GCS). It uses polars to handle the dynamically select the
appropriate type of read/write on a best effort basis.
Example usage for the `YAML API <https://kedro.readthedocs.io/en/stable/data/\
data_catalog_yaml_examples.html>`_:
.. code-block:: yaml
cars:
type: polars.EagerPolarsDataset
file_format: parquet
filepath: s3://data/01_raw/company/cars.parquet
load_args:
low_memory: True
save_args:
compression: "snappy"
Example using Python API:
.. code-block:: pycon
>>> from kedro_datasets.polars import EagerPolarsDataset
>>> import polars as pl
>>>
>>> data = pl.DataFrame({"col1": [1, 2], "col2": [4, 5], "col3": [5, 6]})
>>>
>>> dataset = EagerPolarsDataset(filepath=tmp_path / "test.parquet", file_format="parquet")
>>> dataset.save(data)
>>> reloaded = dataset.load()
>>> assert data.frame_equal(reloaded)
"""
DEFAULT_LOAD_ARGS = {} # type: dict[str, Any]
DEFAULT_SAVE_ARGS = {} # type: dict[str, Any]
[docs]
def __init__( # noqa: PLR0913
self,
*,
filepath: str,
file_format: str,
load_args: dict[str, Any] | None = None,
save_args: dict[str, Any] | None = None,
version: Version | None = None,
credentials: dict[str, Any] | None = None,
fs_args: dict[str, Any] | None = None,
):
"""Creates a new instance of ``EagerPolarsDataset`` pointing to a concrete data file
on a specific filesystem. The appropriate polars load/save methods are dynamically
identified by string matching on a best effort basis.
Args:
filepath: Filepath in POSIX format to a file prefixed with a protocol like
`s3://`.
If prefix is not provided, `file` protocol (local filesystem)
will be used.
The prefix should be any protocol supported by ``fsspec``.
Key assumption: The first argument of either load/save method points to
a filepath/buffer/io type location. There are some read/write targets such
as 'clipboard' or 'records' that will fail since they do not take a filepath
like argument.
file_format: String which is used to match the appropriate load/save method on a
best effort basis. For example if 'csv' is passed, the `polars.read_csv` and
`polars.DataFrame.write_csv` methods will be identified. An error will
be raised unless there is at least one matching `read_<file_format>`
or `write_<file_format>`.
load_args: Polars options for loading CSV files.
Here you can find all available arguments:
https://pola-rs.github.io/polars/py-polars/html/reference/io.html
All defaults are preserved.
save_args: Polars options for saving files.
Here you can find all available arguments:
https://pola-rs.github.io/polars/py-polars/html/reference/io.html
All defaults are preserved.
version: If specified, should be an instance of
``kedro.io.core.Version``. If its ``load`` attribute is
None, the latest version will be loaded. If its ``save``
attribute is None, save version will be autogenerated.
credentials: Credentials required to get access to the underlying filesystem.
E.g. for ``GCSFileSystem`` it should look like `{"token": None}`.
fs_args: Extra arguments to pass into underlying filesystem class constructor
(e.g. `{"project": "my-project"}` for ``GCSFileSystem``).
metadata: Any arbitrary metadata.
This is ignored by Kedro, but may be consumed by users or external plugins.
Raises:
DatasetError: Will be raised if at least less than one appropriate read or write
methods are identified.
"""
self._file_format = file_format.lower()
_fs_args = deepcopy(fs_args) or {}
_fs_open_args_load = _fs_args.pop("open_args_load", {})
_fs_open_args_save = _fs_args.pop("open_args_save", {})
_credentials = deepcopy(credentials) or {}
protocol, path = get_protocol_and_path(filepath)
if protocol == "file":
_fs_args.setdefault("auto_mkdir", True)
self._protocol = protocol
self._fs = fsspec.filesystem(self._protocol, **_credentials, **_fs_args)
super().__init__(
filepath=PurePosixPath(path),
version=version,
exists_function=self._fs.exists,
glob_function=self._fs.glob,
)
self._load_args = deepcopy(self.DEFAULT_LOAD_ARGS)
if load_args is not None:
self._load_args.update(load_args)
self._save_args = deepcopy(self.DEFAULT_SAVE_ARGS)
if save_args is not None:
self._save_args.update(save_args)
_fs_open_args_save.setdefault("mode", "wb")
self._fs_open_args_load = _fs_open_args_load
self._fs_open_args_save = _fs_open_args_save
def _load(self) -> pl.DataFrame:
load_path = get_filepath_str(self._get_load_path(), self._protocol)
load_method = getattr(pl, f"read_{self._file_format}", None)
if not load_method:
raise DatasetError(
f"Unable to retrieve 'polars.read_{self._file_format}' method, please"
" ensure that your "
"'file_format' parameter has been defined correctly as per the Polars"
" API"
" https://pola-rs.github.io/polars/py-polars/html/reference/io.html"
)
with self._fs.open(load_path, **self._fs_open_args_load) as fs_file:
return load_method(fs_file, **self._load_args)
def _save(self, data: pl.DataFrame) -> None:
save_path = get_filepath_str(self._get_save_path(), self._protocol)
save_method = getattr(data, f"write_{self._file_format}", None)
if not save_method:
raise DatasetError(
f"Unable to retrieve 'polars.DataFrame.write_{self._file_format}' "
"method, please "
"ensure that your 'file_format' parameter has been defined correctly as"
" per the Polars API "
"https://pola-rs.github.io/polars/py-polars/html/reference/io.html"
)
buf = BytesIO()
save_method(buf, **self._save_args)
with self._fs.open(save_path, **self._fs_open_args_save) as fs_file:
fs_file.write(buf.getvalue())
self._invalidate_cache()
def _exists(self) -> bool:
try:
load_path = get_filepath_str(self._get_load_path(), self._protocol)
except DatasetError:
return False
return self._fs.exists(load_path)
def _describe(self) -> dict[str, Any]:
return {
"file_format": self._file_format,
"filepath": self._filepath,
"protocol": self._protocol,
"load_args": self._load_args,
"save_args": self._save_args,
"version": self._version,
}
def _release(self) -> None:
super()._release()
self._invalidate_cache()
def _invalidate_cache(self) -> None:
"""Invalidate underlying filesystem caches."""
filepath = get_filepath_str(self._filepath, self._protocol)
self._fs.invalidate_cache(filepath)
