Generator-based operators for asynchronous iteration
aiostream provides a collection of stream operators that can be combined to create asynchronous pipelines of operations.
It can be seen as an asynchronous version of itertools, although some aspects are slightly different. Essentially, all the provided operators return a unified interface called a stream. A stream is an enhanced asynchronous iterable providing the following features:
- Operator pipe-lining - using pipe symbol
|
- Repeatability - every iteration creates a different iterator
- Safe iteration context - using
async with
and thestream
method - Simplified execution - get the last element from a stream using
await
- Slicing and indexing - using square brackets
[]
- Concatenation - using addition symbol
+
The stream operators rely heavily on asynchronous generators (PEP 525):
- python >= 3.6
The stream operators are separated in 7 categories:
creation | iterate, preserve, just, empty, throw, never, repeat, count, range |
transformation | map, enumerate, starmap, cycle, chunks |
selection | take, takelast, skip, skiplast, getitem, filter, takewhile, dropwhile |
combination | map, zip, merge, chain, ziplatest |
aggregation | accumulate, reduce, list |
advanced | concat, flatten, switch, concatmap, flatmap, switchmap |
timing | spaceout, timeout, delay |
miscellaneous | action, print |
The following example demonstrates most of the streams capabilities:
python
import asyncio from aiostream import stream, pipe
async def main():
# Create a counting stream with a 0.2 seconds interval xs = stream.count(interval=0.2)
# Operators can be piped using ' pipe.map(lambda x: x**2)
# Streams can be sliced zs = ys[1:10:2]
# Use a stream context for proper resource management async with zs.stream() as streamer:
# Asynchronous iteration async for z in streamer:
# Print 1, 9, 25, 49 and 81 print('->', z)
# Streams can be awaited and return the last value print('9² = ', await zs)
# Streams can run several times print('9² = ', await zs)
# Streams can be concatenated one_two_three = stream.just(1) + stream.range(2, 4)
# Print [1, 2, 3] print(await stream.list(one_two_three))
# Run main coroutine loop = asyncio.get_event_loop() loop.run_until_complete(main()) loop.close()
More examples are available in the example section of the documentation.
Vincent Michel: vxgmichel@gmail.com