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aiofiles: file support for asyncio

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aiofiles is an Apache2 licensed library, written in Python, for handling local disk files in asyncio applications.

Ordinary local file IO is blocking, and cannot easily and portably be made asynchronous. This means doing file IO may interfere with asyncio applications, which shouldn't block the executing thread. aiofiles helps with this by introducing asynchronous versions of files that support delegating operations to a separate thread pool.

async with aiofiles.open('filename', mode='r') as f:
    contents = await f.read()
print(contents)
'My file contents'

Asynchronous iteration is also supported.

async with aiofiles.open('filename') as f:
    async for line in f:
        ...

Asynchronous interface to tempfile module.

async with aiofiles.tempfile.TemporaryFile('wb') as f:
    await f.write(b'Hello, World!')

Features

  • a file API very similar to Python's standard, blocking API
  • support for buffered and unbuffered binary files, and buffered text files
  • support for async/await (PEP 492) constructs
  • async interface to tempfile module

Installation

To install aiofiles, simply:

$ pip install aiofiles

Usage

Files are opened using the aiofiles.open() coroutine, which in addition to mirroring the builtin open accepts optional loop and executor arguments. If loop is absent, the default loop will be used, as per the set asyncio policy. If executor is not specified, the default event loop executor will be used.

In case of success, an asynchronous file object is returned with an API identical to an ordinary file, except the following methods are coroutines and delegate to an executor:

  • close
  • flush
  • isatty
  • read
  • readall
  • read1
  • readinto
  • readline
  • readlines
  • seek
  • seekable
  • tell
  • truncate
  • writable
  • write
  • writelines

In case of failure, one of the usual exceptions will be raised.

aiofiles.stdin, aiofiles.stdout, aiofiles.stderr, aiofiles.stdin_bytes, aiofiles.stdout_bytes, and aiofiles.stderr_bytes provide async access to sys.stdin, sys.stdout, sys.stderr, and their corresponding .buffer properties.

The aiofiles.os module contains executor-enabled coroutine versions of several useful os functions that deal with files:

  • stat
  • statvfs
  • sendfile
  • rename
  • renames
  • replace
  • remove
  • unlink
  • mkdir
  • makedirs
  • rmdir
  • removedirs
  • link
  • symlink
  • readlink
  • listdir
  • scandir
  • access
  • getcwd
  • path.abspath
  • path.exists
  • path.isfile
  • path.isdir
  • path.islink
  • path.ismount
  • path.getsize
  • path.getatime
  • path.getctime
  • path.samefile
  • path.sameopenfile

Tempfile

aiofiles.tempfile implements the following interfaces:

  • TemporaryFile
  • NamedTemporaryFile
  • SpooledTemporaryFile
  • TemporaryDirectory

Results return wrapped with a context manager allowing use with async with and async for.

async with aiofiles.tempfile.NamedTemporaryFile('wb+') as f:
    await f.write(b'Line1\n Line2')
    await f.seek(0)
    async for line in f:
        print(line)

async with aiofiles.tempfile.TemporaryDirectory() as d:
    filename = os.path.join(d, "file.ext")

Writing tests for aiofiles

Real file IO can be mocked by patching aiofiles.threadpool.sync_open as desired. The return type also needs to be registered with the aiofiles.threadpool.wrap dispatcher:

aiofiles.threadpool.wrap.register(mock.MagicMock)(
    lambda *args, **kwargs: aiofiles.threadpool.AsyncBufferedIOBase(*args, **kwargs)
)

async def test_stuff():
    write_data = 'data'
    read_file_chunks = [
        b'file chunks 1',
        b'file chunks 2',
        b'file chunks 3',
        b'',
    ]
    file_chunks_iter = iter(read_file_chunks)

    mock_file_stream = mock.MagicMock(
        read=lambda *args, **kwargs: next(file_chunks_iter)
    )

    with mock.patch('aiofiles.threadpool.sync_open', return_value=mock_file_stream) as mock_open:
        async with aiofiles.open('filename', 'w') as f:
            await f.write(write_data)
            assert await f.read() == b'file chunks 1'

        mock_file_stream.write.assert_called_once_with(write_data)

History

24.1.0 (2024-06-24)

  • Import os.link conditionally to fix importing on android. #175
  • Remove spurious items from aiofiles.os.__all__ when running on Windows.
  • Switch to more modern async idioms: Remove types.coroutine and make AiofilesContextManager an awaitable instead a coroutine.
  • Add aiofiles.os.path.abspath and aiofiles.os.getcwd. #174
  • aiofiles is now tested on Python 3.13 too. #184
  • Dropped Python 3.7 support. If you require it, use version 23.2.1.

23.2.1 (2023-08-09)

  • Import os.statvfs conditionally to fix importing on non-UNIX systems. #171 #172
  • aiofiles is now also tested on Windows.

23.2.0 (2023-08-09)

  • aiofiles is now tested on Python 3.12 too. #166 #168
  • On Python 3.12, aiofiles.tempfile.NamedTemporaryFile now accepts a delete_on_close argument, just like the stdlib version.
  • On Python 3.12, aiofiles.tempfile.NamedTemporaryFile no longer exposes a delete attribute, just like the stdlib version.
  • Added aiofiles.os.statvfs and aiofiles.os.path.ismount. #162
  • Use PDM instead of Poetry. #169

23.1.0 (2023-02-09)

  • Added aiofiles.os.access. #146
  • Removed aiofiles.tempfile.temptypes.AsyncSpooledTemporaryFile.softspace. #151
  • Added aiofiles.stdin, aiofiles.stdin_bytes, and other stdio streams. #154
  • Transition to asyncio.get_running_loop (vs asyncio.get_event_loop) internally.

22.1.0 (2022-09-04)

  • Added aiofiles.os.path.islink. #126
  • Added aiofiles.os.readlink. #125
  • Added aiofiles.os.symlink. #124
  • Added aiofiles.os.unlink. #123
  • Added aiofiles.os.link. #121
  • Added aiofiles.os.renames. #120
  • Added aiofiles.os.{listdir, scandir}. #143
  • Switched to CalVer.
  • Dropped Python 3.6 support. If you require it, use version 0.8.0.
  • aiofiles is now tested on Python 3.11.

0.8.0 (2021-11-27)

  • aiofiles is now tested on Python 3.10.
  • Added aiofiles.os.replace. #107
  • Added aiofiles.os.{makedirs, removedirs}.
  • Added aiofiles.os.path.{exists, isfile, isdir, getsize, getatime, getctime, samefile, sameopenfile}. #63
  • Added suffix, prefix, dir args to aiofiles.tempfile.TemporaryDirectory. #116

0.7.0 (2021-05-17)

  • Added the aiofiles.tempfile module for async temporary files. #56
  • Switched to Poetry and GitHub actions.
  • Dropped 3.5 support.

0.6.0 (2020-10-27)

  • aiofiles is now tested on ppc64le.
  • Added name and mode properties to async file objects. #82
  • Fixed a DeprecationWarning internally. #75
  • Python 3.9 support and tests.

0.5.0 (2020-04-12)

  • Python 3.8 support. Code base modernization (using async/await instead of asyncio.coroutine/yield from).
  • Added aiofiles.os.remove, aiofiles.os.rename, aiofiles.os.mkdir, aiofiles.os.rmdir. #62

0.4.0 (2018-08-11)

  • Python 3.7 support.
  • Removed Python 3.3/3.4 support. If you use these versions, stick to aiofiles 0.3.x.

0.3.2 (2017-09-23)

  • The LICENSE is now included in the sdist. #31

0.3.1 (2017-03-10)

  • Introduced a changelog.
  • aiofiles.os.sendfile will now work if the standard os module contains a sendfile function.

Contributing

Contributions are very welcome. Tests can be run with tox, please ensure the coverage at least stays the same before you submit a pull request.