file_io

FileIO

class FileIO(typing.Generic)

[Alpha] FileIO handle, used in the Sandbox filesystem API.

Deprecated on 2026-03-09. Use the Sandbox.filesystem APIs instead.

The API is designed to mimic Python's io.FileIO.

Currently this API is in Alpha and is subject to change. File I/O operations may be limited in size to 100 MiB, and the throughput of requests is restricted in the current implementation. For our recommendations on large file transfers see the Sandbox filesystem access guide.

Usage

import modal

app = modal.App.lookup("my-app", create_if_missing=True)

sb = modal.Sandbox.create(app=app)
f = sb.open("/tmp/foo.txt", "w")
f.write("hello")
f.close()

__init__(self, client, task_id)

create

create(cls, path, mode, client, task_id)

Create a new FileIO handle.

read

read(self, n=None)

Read n bytes from the current position, or the entire remaining file if n is None.

readline

readline(self)

Read a single line from the current position.

readlines

readlines(self)

Read all lines from the current position.

write

write(self, data)

Write data to the current position.

Writes may not appear until the entire buffer is flushed, which can be done manually with flush() or automatically when the file is closed.

flush

flush(self)

Flush the buffer to disk.

seek

seek(self, offset, whence=0)

Move to a new position in the file.

whence defaults to 0 (absolute file positioning); other values are 1 (relative to the current position) and 2 (relative to the file's end).

ls

ls(cls, path, client, task_id)

List the contents of the provided directory.

mkdir

mkdir(cls, path, client, task_id, parents=False)

Create a new directory.

rm

rm(cls, path, client, task_id, recursive=False)

Remove a file or directory in the Sandbox.

watch

watch(cls, path, client, task_id, filter=None, recursive=False, timeout=None)

close

close(self)

Flush the buffer and close the file.

ls

ls(path, client, task_id)

List the contents of the provided directory.

mkdir

mkdir(path, client, task_id, parents=False)

Create a new directory.

rm

rm(path, client, task_id, recursive=False)

Remove a file or directory in the Sandbox.

watch

watch(path, client, task_id, filter=None, recursive=False, timeout=None)

Watch a file or directory for changes.