Asynchronous file I/O support

AnyIO provides asynchronous wrappers for blocking file operations. These wrappers run blocking operations in worker threads.

Example:

from anyio import open_file, run


async def main():
    async with await open_file('/some/path/somewhere') as f:
        contents = await f.read()
        print(contents)

run(main)

The wrappers also support asynchronous iteration of the file line by line, just as the standard file objects support synchronous iteration:

from anyio import open_file, run


async def main():
    async with await open_file('/some/path/somewhere') as f:
        async for line in f:
            print(line, end='')

run(main)

To wrap an existing open file object as an asynchronous file, you can use wrap_file():

from anyio import wrap_file, run


async def main():
    with open('/some/path/somewhere') as f:
        async for line in wrap_file(f):
            print(line, end='')

run(main)

Note

Closing the wrapper also closes the underlying synchronous file object.

See also

File streams

Asynchronous path operations

AnyIO provides an asynchronous version of the pathlib.Path class. It differs with the original in a number of ways:

• Operations that perform disk I/O (like read_bytes()) are run in a worker thread and thus require an await

• Methods like glob() return an asynchronous iterator that yields asynchronous Path objects

• Properties and methods that normally return pathlib.Path objects return Path objects instead

• Methods and properties from the Python 3.10 API are available on all versions

• Use as a context manager is not supported, as it is deprecated in pathlib

For example, to create a file with binary content:

from anyio import Path, run


async def main():
    path = Path('/foo/bar')
    await path.write_bytes(b'hello, world')

run(main)

Asynchronously iterating a directory contents can be done as follows:

from anyio import Path, run


async def main():
    # Print the contents of every file (assumed to be text) in the directory /foo/bar
    dir_path = Path('/foo/bar')
    async for path in dir_path.iterdir():
        if await path.is_file():
            print(await path.read_text())
            print('---------------------')

run(main)