aiofiles: file support for asyncio

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
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: threadpool.AsyncBufferedIOBase(*args, **kwargs))

async def test_stuff():
    data = 'data'
    mock_file = mock.MagicMock()

    with mock.patch('aiofiles.threadpool.sync_open', return_value=mock_file) as mock_open:
        async with aiofiles.open('filename', 'w') as f:
            await f.write(data)

        mock_file.write.assert_called_once_with(data)

History

23.2.1 (2023-08-09)

Import os.statvfs conditionally to fix importing on non-UNIX systems. #171 #172

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