aio

aiostream

Generator-based operators for asynchronous iteration

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aiostream

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Generator-based operators for asynchronous iteration

Synopsis

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 the stream method
  • Simplified execution - get the last element from a stream using await
  • Slicing and indexing - using square brackets []
  • Concatenation - using addition symbol +

Requirements

The stream operators rely heavily on asynchronous generators (PEP 525_):

  • python >= 3.6

Stream operators

The stream operators_ are separated in 7 categories:

+--------------------+---------------------------------------------------------------------------------------+ | creation | iterate, preserve, just, call, empty, throw, never, repeat, count, range | +--------------------+---------------------------------------------------------------------------------------+ | transformation | map, enumerate, starmap, cycle, chunks | +--------------------+---------------------------------------------------------------------------------------+ | selection | take, takelast, skip, skiplast, getitem, filter, until, 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_ | +--------------------+---------------------------------------------------------------------------------------+

Demonstration

The following example demonstrates most of the streams capabilities:

.. sourcecode:: 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 '|'
    ys = xs | 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.

Contact

Vincent Michel: vxgmichel@gmail.com

.. _aiostream: https://github.com/vxgmichel/aiostream .. _PEP 525: http://www.python.org/dev/peps/pep-0525/ .. _Rx: http://reactivex.io/ .. _aioreactive: http://github.com/dbrattli/aioreactive .. _itertools: http://docs.python.org/3/library/itertools.html

.. _stream operators: http://aiostream.readthedocs.io/en/latest/operators.html .. _example section: http://aiostream.readthedocs.io/en/latest/examples.html

.. _iterate: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.iterate .. _preserve: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.preserve .. _just: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.just .. _call: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.call .. _throw: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.throw .. _empty: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.empty .. _never: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.never .. _repeat: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.repeat .. _range: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.range .. _count: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.count

.. _map: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.map .. _enumerate: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.enumerate .. _starmap: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.starmap .. _cycle: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.cycle .. _chunks: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.chunks

.. _take: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.take .. _takelast: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.takelast .. _skip: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.skip .. _skiplast: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.skiplast .. _getitem: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.getitem .. _filter: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.filter .. _until: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.until .. _takewhile: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.takewhile .. _dropwhile: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.dropwhile

.. _chain: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.chain .. _zip: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.zip .. _merge: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.merge .. _ziplatest: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.ziplatest

.. _accumulate: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.accumulate .. _reduce: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.reduce .. _list: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.list

.. _concat: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.concat .. _flatten: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.flatten .. _switch: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.switch .. _concatmap: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.concatmap .. _flatmap: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.flatmap .. _switchmap: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.switchmap

.. _spaceout: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.spaceout .. _delay: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.delay .. _timeout: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.timeout

.. _action: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.action .. _print: http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.print

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