Metadata-Version: 2.1
Name: aioresult
Version: 0.9
Summary: Capture the result of a Trio or anyio task
Author: Arthur Tacca
License: Boost Software License - Version 1.0 - August 17th, 2003
        
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Project-URL: repository, https://github.com/arthur-tacca/aioresult
Project-URL: documentation, https://aioresult.readthedocs.io/en/stable/docs.html
Keywords: async,anyio,trio,result,future,nursery,taskgroup
Classifier: Development Status :: 5 - Production/Stable
Classifier: Framework :: AnyIO
Classifier: Framework :: Trio
Classifier: Intended Audience :: Developers
Classifier: License :: OSI Approved :: Boost Software License 1.0 (BSL-1.0)
Classifier: Operating System :: OS Independent
Classifier: Programming Language :: Python :: 3 :: Only
Classifier: Programming Language :: Python :: 3.8
Classifier: Programming Language :: Python :: 3.9
Classifier: Programming Language :: Python :: 3.10
Classifier: Programming Language :: Python :: 3.11
Classifier: Programming Language :: Python :: Implementation :: CPython
Classifier: Programming Language :: Python :: Implementation :: PyPy
Classifier: Topic :: System :: Networking
Requires-Python: >=3.7
Description-Content-Type: text/x-rst
Provides-Extra: docs
License-File: LICENSE

aioresult: Capture the result of a Trio or anyio task
=====================================================

Welcome to aioresult! This is a very small library to capture the result of an asynchronous
operation, either an async function (with the ``ResultCapture`` class) or more generally (with the
``Future`` class). It works with `Trio nurseries
<https://trio.readthedocs.io/en/stable/reference-core.html#nurseries-and-spawning>`__ and `anyio
task groups <https://anyio.readthedocs.io/en/stable/tasks.html>`__. It is not needed for Python 3.11
`asyncio task groups <https://docs.python.org/3/library/asyncio-task.html#task-groups>`__ because
those already return an object representing the task, allowing the result to be retrieved.

The code is hosted on github: https://github.com/arthur-tacca/aioresult

Documentation is on ReadTheDocs: https://aioresult.readthedocs.io/en/stable/docs.html


Quick Overview
--------------

The ``ResultCapture`` class runs an async function in a nursery and stores its return value (or
raised exception) for later::

    async with trio.open_nursery() as n:
        result1 = ResultCapture.start_soon(n, foo, 1)
        result2 = ResultCapture.start_soon(n, foo, 2)
    # At this point the tasks have completed, and results are stashed in ResultCapture objects
    print("results", result1.result(), result2.result())

When stored in list, the effect is very similar to the `asyncio gather() function
<https://docs.python.org/3/library/asyncio-task.html#asyncio.gather>`__::

    async with trio.open_nursery() as n:
        results = [aioresult.ResultCapture.start_soon(n, foo, i) for i in range(10)]
    print("results:", *[r.result() for r in results])


.. note:: A key design decision about the ``ResultCapture`` class is that **exceptions are allowed
  to propagate out of the task into their enclosing nursery**. This is unlike some similar
  libraries, which consume the exception in its original context and rethrow it later. In practice,
  aioresult's behaviour is simpler and less error prone.

There is also a derived class ``StartableResultCapture``, meant for async functions that satisfy
`the Trio task start protocol
<https://trio.readthedocs.io/en/stable/reference-core.html#trio.Nursery.start>`__.

There is also a simple ``Future`` class that shares a lot of its code with ``ResultCapture``. The
result is retrieved the same way, but it is set explicitly rather than captured from a task. It is
most often used when an API wants to return a value that will be demultiplexed from a shared
connection::

    # When making a request, create a future, store it for later and return to caller
    f = aioresult.Future()

    # The result is set, usually inside a networking API
    f.set_result(result)

    # The calling code can wait for the result then retrieve it
    await f.wait_done()
    print("result:", f.result())

The interface in ``Future`` and ``ResultCapture`` to wait for a result and retrieve it is shared in
a base class ``ResultBase``.


Installation and Usage
----------------------

Install into a suitable virtual environment with ``pip``::

    pip install aioresult

aioresult can be used with Trio nurseries::

    import trio
    from aioresult import ResultCapture

    async def wait_and_return(i):
        await trio.sleep(i)
        return i

    async def use_aioresult():
        async with trio.open_nursery() as n:
            results = [ResultCapture.start_soon(n, wait_and_return, i) for i in range(5)]
        print("results:", *[r.result() for r in results])

    if __name__ == "__main__":
        trio.run(use_aioresult)

It can also be used with anyio task groups::

    import asyncio
    import anyio
    from aioresult import ResultCapture

    async def wait_and_return(i):
        await anyio.sleep(i)
        return i

    async def use_aioresult():
         async with anyio.create_task_group() as tg:
             results = [ResultCapture.start_soon(tg, wait_and_return, i) for i in range(5)]
         print("results:", *[r.result() for r in results])

    if __name__ == "__main__":
        asyncio.run(use_aioresult())


Running the Tests
-----------------

The automated tests are currently not run through any automated pipeline. To run them yourself,
start by installing the dependencies::

    pip install pytest coverage anyio trio

To just run the tests, run ``pytest`` in the root of the repository::

    python -m pytest

To also get coverage information, run it with the ``coverage`` command::

    coverage run -m pytest

You can then use ``coverage html`` to get a nice HTML output of exactly what code has been tested
and what has been missed.


License
-------

Copyright Arthur Tacca 2022

Distributed under the Boost Software License, Version 1.0.
See accompanying file LICENSE or the copy at https://www.boost.org/LICENSE_1_0.txt

This is similar to other liberal licenses like MIT and BSD: you can use this library without the
need to share your program's source code, so long as you provide attribution of aioresult.

The Boost license has the additional provision that you do not even need to provide attribution if
you are distributing your software in binary form only, e.g. if you have compiled to an executable
with `Nuitka <https://nuitka.net/>`__.  (Bundlers like `pyinstaller <https://pyinstaller.org/>`__
and `py2exe <https://www.py2exe.org/>`__ don't count for this because they still include the source
code internally.)
