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Asynchronous file I/O support
=============================
.. py:currentmodule:: anyio
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
:func:`.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.
.. seealso:: :ref:`FileStreams`
Asynchronous path operations
----------------------------
AnyIO provides an asynchronous version of the :class:`pathlib.Path` class. It differs
with the original in a number of ways:
* Operations that perform disk I/O (like :meth:`~pathlib.Path.read_bytes`) are run in a
worker thread and thus require an ``await``
* Methods like :meth:`~pathlib.Path.glob` return an asynchronous iterator that yields
asynchronous :class:`~.Path` objects
* Properties and methods that normally return :class:`pathlib.Path` objects return
:class:`~.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)
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