class flytekit.types.file.FlyteFile(path: str, downloader: Callable = <function noop>, remote_path=None)[source]

Since there is no native Python implementation of files and directories for the Flyte Blob type, (like how int exists for Flyte’s Integer type) we need to create one so that users can express that their tasks take in or return a file.

There are a few possible types on the Python side that can be specified:

  • typing.IO Usually this takes the form of TextIO or BinaryIO. For now we only support these derived classes. This is what open() will generally return. For example,

    def get_read_file_handle() -> TextIO:
        fh = open(__file__, 'r')
        return fh
    def get_bin_read_file_handle() -> BinaryIO:
        fh = open(__file__, 'rb')
        return fh

    Note: issubclass(type(fh), typing.Text/BinaryIO) is False for some reason, nevertheless the type checker passes.

    If you specify either of these, as an input, Flyte will open a filehandle to the data, before the task runs, and pass that handle as the argument to your function. If you specify it as an output, Flyte will read() the data after the task completes, and write it to Flyte’s configurable Blob store. On the backend, Flyte’s type system for file and file-like objects include a str based “format” as part of the type. For TextIO and BinaryIO, the format will be “TextIO” and “BinaryIO”. These IO types have a higher likelihood of being subject to change before an official, release. The PathLike types will not.

  • os.PathLike This is just a path on the filesystem accessible from the Python process. This is a native Python abstract class.

    def path_task() -> os.PathLike:
        return '/tmp/xyz.txt'

    If you specify a PathLike as an input, the task will receive a PathLike at task start, and you can open() it as normal. However, since we want to control when files are downloaded, Flyte provides its own PathLike object:

    from flytekit import types as flytekit_typing
    def t1(in1: flytekit_typing.FlyteFile) -> str:
        with open(in1, 'r') as fh:
            lines = fh.readlines()
            return "".join(lines)

    As mentioned above, since Flyte file types have a string embedded in it as part of the type, you can add a format by specifying a string after the class like so.

    def t2() -> flytekit_typing.FlyteFile["csv"]:
        from random import sample
        sequence = [i for i in range(20)]
        subset = sample(sequence, 5)
        results = ",".join([str(x) for x in subset])
        with open("/tmp/blah.csv", "w") as fh:
        return "/tmp/blah.csv"

How are these files handled?

S3, http, https are all treated as remote - the behavior should be the same, they are never copied unless explicitly told to do so.

Local paths always get uploaded, unless explicitly told not to do so.

If you specify a path as a string, you get the default behavior, not possible to override. To override, you must use the FlyteFile class.

More succinctly, regardless of whether it is input or output, these rules apply:
  • "s3://bucket/path" -> will never get uploaded

  • "" -> will never get uploaded

  • "/tmp/blah" -> will always get uploaded

To specify non-default behavior:

  • Copy the s3 path to a new location. FlyteFilePath("s3://bucket/path", remote_path=True)

  • Copy the s3 path to a specific location. FlyteFilePath("s3://bucket/path", remote_path="s3://other-bucket/path")

  • Copy local path to a specific location. FlyteFilePath("/tmp/blah", remote_path="s3://other-bucket/path")

  • Do not copy local path, this will copy the string into the literal. For example, let’s say your docker image has a thousand files in it, and you want to tell the next task, which file to look at. (Bad example, you shouldn’t have that many files in your image.) FlyteFilePath("/tmp/blah", remote_path=False)

  • However, we have a shorthand. “file:///tmp/blah” is treated as “remote” and is by default not copied.

__init__(path: str, downloader: Callable = <function noop>, remote_path=None)[source]
  • path – The source path that users are expected to call open() on

  • downloader – Optional function that can be passed that used to delay downloading of the actual fil until a user actually calls open().

  • remote_path – If the user wants to return something and also specify where it should be uploaded to.


__init__(path[, downloader, remote_path])

param path

The source path that users are expected to call open() on







//something, flytekit will download the file for the user.