ray.data.read_csv#

ray.data.read_csv(paths: Union[str, List[str]], *, filesystem: Optional[pyarrow.fs.FileSystem] = None, parallelism: int = - 1, ray_remote_args: Dict[str, Any] = None, arrow_open_stream_args: Optional[Dict[str, Any]] = None, meta_provider: Optional[ray.data.datasource.file_meta_provider.BaseFileMetadataProvider] = None, partition_filter: Optional[ray.data.datasource.partitioning.PathPartitionFilter] = None, partitioning: ray.data.datasource.partitioning.Partitioning = Partitioning(style='hive', base_dir='', field_names=None, filesystem=None), ignore_missing_paths: bool = False, **arrow_csv_args) → ray.data.dataset.Dataset[source]#

Creates a Dataset from CSV files.

Examples

Read a file in remote storage.

>>> import ray
>>> ds = ray.data.read_csv("s3://anonymous@ray-example-data/iris.csv")
>>> ds.schema()
Column             Type
------             ----
sepal length (cm)  double
sepal width (cm)   double
petal length (cm)  double
petal width (cm)   double
target             int64

Read multiple local files.

>>> ray.data.read_csv( 
...    ["local:///path/to/file1", "local:///path/to/file2"])

Read a directory from remote storage.

>>> ds = ray.data.read_csv("s3://anonymous@ray-example-data/iris-csv/")

Read files that use a different delimiter. For more uses of ParseOptions see https://arrow.apache.org/docs/python/generated/pyarrow.csv.ParseOptions.html # noqa: #501

>>> from pyarrow import csv
>>> parse_options = csv.ParseOptions(delimiter="\t")
>>> ds = ray.data.read_csv(
...     "s3://anonymous@ray-example-data/iris.tsv",
...     parse_options=parse_options)
>>> ds.schema()
Column        Type
------        ----
sepal.length  double
sepal.width   double
petal.length  double
petal.width   double
variety       string

Convert a date column with a custom format from a CSV file. For more uses of ConvertOptions see https://arrow.apache.org/docs/python/generated/pyarrow.csv.ConvertOptions.html # noqa: #501

>>> from pyarrow import csv
>>> convert_options = csv.ConvertOptions(
...     timestamp_parsers=["%m/%d/%Y"])
>>> ds = ray.data.read_csv(
...     "s3://anonymous@ray-example-data/dow_jones.csv",
...     convert_options=convert_options)

By default, read_csv() parses Hive-style partitions from file paths. If your data adheres to a different partitioning scheme, set the partitioning parameter.

>>> ds = ray.data.read_csv("s3://anonymous@ray-example-data/year=2022/month=09/sales.csv")
>>> ds.take(1)
[{'order_number': 10107, 'quantity': 30, 'year': '2022', 'month': '09'}]

By default, read_csv() reads all files from file paths. If you want to filter files by file extensions, set the partition_filter parameter.

Read only *.csv files from a directory.

>>> from ray.data.datasource import FileExtensionFilter
>>> ray.data.read_csv("s3://anonymous@ray-example-data/different-extensions/",
...     partition_filter=FileExtensionFilter("csv"))
Dataset(num_blocks=..., num_rows=1, schema={a: int64, b: int64})
Parameters

  • paths – A single file or directory, or a list of file or directory paths. A list of paths can contain both files and directories.

  • filesystem – The PyArrow filesystem implementation to read from. These filesystems are specified in the pyarrow docs. Specify this parameter if you need to provide specific configurations to the filesystem. By default, the filesystem is automatically selected based on the scheme of the paths. For example, if the path begins with s3://, the S3FileSystem is used.

  • parallelism – The amount of parallelism to use for the dataset. Defaults to -1, which automatically determines the optimal parallelism for your configuration. You should not need to manually set this value in most cases. For details on how the parallelism is automatically determined and guidance on how to tune it, see Tuning read parallelism. Parallelism is upper bounded by the total number of records in all the CSV files.

  • ray_remote_args – kwargs passed to remote() in the read tasks.

  • arrow_open_stream_args – kwargs passed to pyarrow.fs.FileSystem.open_input_file. when opening input files to read.

  • meta_provider – A file metadata provider. Custom metadata providers may be able to resolve file metadata more quickly and/or accurately. In most cases, you do not need to set this. If None, this function uses a system-chosen implementation.

  • partition_filter – A PathPartitionFilter. Use with a custom callback to read only selected partitions of a dataset. By default, no files are filtered. To filter out all file paths except those whose file extension matches e.g., “.csv”, you can provide a FileExtensionFilter.

  • partitioning –

    A Partitioning object that describes how paths are organized. By default, this function parses Hive-style partitions.

  • ignore_missing_paths – If True, ignores any file paths in paths that are not found. Defaults to False.

  • arrow_csv_args – CSV read options to pass to pyarrow.csv.open_csv when opening CSV files.

Returns

Dataset producing records read from the specified paths.

PublicAPI: This API is stable across Ray releases.