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Asynchronous `zip` like aggregator for `async for`

Project description

AsyncZip is a simple zip like function working with asynchronous iterables. It look, in many aspects, like asyncio.wait.

Usage

Given n asynchronous iterables, AsyncZip(*aiterables) gives a new asynchronous iterable iterating over all of them. Like asyncio.wait, it’s possible to wait for any iterable to yield something using the option FIRST_COMPLETED, or to wait for all of them using the option ALL_COMPLETED.

class AsyncZip

def __init__(self, *asynchronous_iterables, loop=None, yield_when=FIRST_COMPLETED):
  • asynchronous_iterables: A collection of asynchronous iterables
  • loop: Optional named parameter, to give an specific event loop
  • yield_when: Like return_when from asyncio.wait, FIRST_COMPLETED or ALL_COMPLETED.

FIRST_COMPLETED, ALL_COMPLETED

The two values yield_when can take, FIRST_COMPLETED and ALL_COMPLETED tell, like for asyncio.wait, when AsyncZip should yield. Defaults to FIRST_COMPLETED.

  • FIRST_COMPLETED

Like select, where AsyncZip yields each time any iterable yields, as soon as possible.

  • ALL_COMPLETED

It’s the classical zip mode, where AsyncZip waits for a value for each iterator before yielding them all in a single loop.

Example usage

import asyncio
from asynczip import AsyncZip

class DummyAsyncIterable:
    def __init__(self, items):
        self.items = items

    async def __aiter__(self):
        return self

    async def __anext__(self):
        try:
            return self.items.pop(0)
        except IndexError:
            raise StopAsyncIteration

async def test():
    async for items in AsyncZip(DummyAsyncIterable(list("foo")),
                                DummyAsyncIterable(list("bar"))):
        print(items)

asyncio.get_event_loop().run_until_complete(test())

Gives:

[<Task finished coro=<DummyAsyncIterable.__anext__() done, defined at test.py:11> result='f'>,<Task finished coro=<DummyAsyncIterable.__anext__() done, defined at test.py:11> result='b'>]
[<Task finished coro=<DummyAsyncIterable.__anext__() done, defined at test.py:11> result='o'>, <Task finished coro=<DummyAsyncIterable.__anext__() done, defined at test.py:11> result='a'>]
[<Task finished coro=<DummyAsyncIterable.__anext__() done, defined at test.py:11> result='o'>, <Task finished coro=<DummyAsyncIterable.__anext__() done, defined at test.py:11> result='r'>]

Project details


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