Asynchronous file operations.
Project description
Real asynchronous file operations with asyncio support.
Status
Development - Stable
Features
Since version 2.0.0 using caio, is contain linux libaio and two thread-based implementations (c-based and pure-python).
AIOFile has no internal pointer. You should pass offset and chunk_size for each operation or use helpers (Reader or Writer).
For Linux using implementation based on libaio.
For POSIX (MacOS X and optional Linux) using implementation using on threadpool.
Otherwise using pure-python thread-based implementation.
Implementation chooses automatically depending on system compatibility.
Code examples
All code examples requires python 3.6+.
High-level API
async_open helper
The async_open helper creates file like object with file-like methods:
import asyncio
from aiofile import async_open
async def main():
async with async_open("/tmp/hello.txt", 'w+') as afp:
await afp.write("Hello ")
await afp.write("world")
afp.seek(0)
print(await afp.read())
loop = asyncio.get_event_loop()
loop.run_until_complete(main())Supported methods:
async def read(length = -1) - reading chunk from file, when length is -1 will read whole file.
async def write(data) - write chunk to file
def seek(offset) - set file pointer position
def tell() - returns current file pointer position
Reader and Writer
import asyncio
from aiofile import AIOFile, Reader, Writer
async def main():
async with AIOFile("/tmp/hello.txt", 'w+') as afp:
writer = Writer(afp)
reader = Reader(afp, chunk_size=8)
await writer("Hello")
await writer(" ")
await writer("World")
await afp.fsync()
async for chunk in reader:
print(chunk)
loop = asyncio.get_event_loop()
loop.run_until_complete(main())LineReader - read file line by line
import asyncio
from aiofile import AIOFile, LineReader, Writer
async def main():
async with AIOFile("/tmp/hello.txt", 'w+') as afp:
writer = Writer(afp)
await writer("Hello")
await writer(" ")
await writer("World")
await writer("\n")
await writer("\n")
await writer("From async world")
await afp.fsync()
async for line in LineReader(afp):
print(line)
loop = asyncio.get_event_loop()
loop.run_until_complete(main())Low-level API
Following API is just little bit sugared caio API.
Write and Read
import asyncio
from aiofile import AIOFile
async def main():
async with AIOFile("/tmp/hello.txt", 'w+') as afp:
await afp.write("Hello ")
await afp.write("world", offset=7)
await afp.fsync()
print(await afp.read())
loop = asyncio.get_event_loop()
loop.run_until_complete(main())Read file line by line
import asyncio
from aiofile import AIOFile, LineReader, Writer
async def main():
async with AIOFile("/tmp/hello.txt", 'w') as afp:
writer = Writer(afp)
for i in range(10):
await writer("%d Hello World\n" % i)
await writer("Tail-less string")
async with AIOFile("/tmp/hello.txt", 'r') as afp:
async for line in LineReader(afp):
print(line[:-1])
loop = asyncio.get_event_loop()
loop.run_until_complete(main())More examples
Useful examples with aiofile
Async CSV Dict Reader
import asyncio
import io
from csv import DictReader
from aiofile import AIOFile, LineReader
class AsyncDictReader:
def __init__(self, afp, **kwargs):
self.buffer = io.BytesIO()
self.file_reader = LineReader(
afp, line_sep=kwargs.pop('line_sep', '\n'),
chunk_size=kwargs.pop('chunk_size', 4096),
offset=kwargs.pop('offset', 0),
)
self.reader = DictReader(
io.TextIOWrapper(
self.buffer,
encoding=kwargs.pop('encoding', 'utf-8'),
errors=kwargs.pop('errors', 'replace'),
), **kwargs,
)
self.line_num = 0
def __aiter__(self):
return self
async def __anext__(self):
if self.line_num == 0:
header = await self.file_reader.readline()
self.buffer.write(header)
line = await self.file_reader.readline()
if not line:
raise StopAsyncIteration
self.buffer.write(line)
self.buffer.seek(0)
try:
result = next(self.reader)
except StopIteration as e:
raise StopAsyncIteration from e
self.buffer.seek(0)
self.buffer.truncate(0)
self.line_num = self.reader.line_num
return result
async def main():
async with AIOFile('sample.csv', 'rb') as afp:
async for item in AsyncDictReader(afp, line_sep='\r'):
print(item)
loop = asyncio.new_event_loop()
asyncio.set_event_loop(loop)
try:
loop.run_until_complete(main())
finally:
# Shutting down and closing file descriptors after interrupt
loop.run_until_complete(loop.shutdown_asyncgens())
loop.close()Release history Release notifications | RSS feed
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