# txaio

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txaio is a helper library for writing code that runs unmodified on both Twisted and asyncio / Trollius.

This is like six, but for wrapping over differences between Twisted and asyncio so one can write code that runs unmodified on both (aka source code compatibility). In other words: your users can choose if they want asyncio or Twisted as a dependency.

Note that, with this approach, user code runs under the native event loop of either Twisted or asyncio. This is different from attaching either one’s event loop to the other using some event loop adapter.

## Platform support

txaio runs on CPython 3.6+ and PyPy 3, on top of Twisted or asyncio. Specifically, txaio is tested on the following platforms:

- CPython 3.6 and 3.9 on Twisted 18.7, 19.10, trunk and on asyncio (stdlib)

- PyPy 3.6 an 3.7 on Twisted 18.7, 19.10, trunk and on asyncio (stdlib)

> Note: txaio up to version 18.8.1 also supported Python 2.7 and Python 3.4. Beginning with release v20.1.1, txaio only supports Python 3.5+. Beginning with release v20.12.1, txaio only supports Python 3.6+.

## How it works

Instead of directly importing, instantiating and using `Deferred` (for Twisted) or `Future` (for asyncio) objects, txaio provides helper-functions to do that for you, as well as associated things like adding callbacks or errbacks.

This obviously changes the style of your code, but then you can choose at runtime (or import time) which underlying event-loop to use. This means you can write one code-base that can run on Twisted or asyncio (without a Twisted dependency) as you or your users see fit.

Code like the following can then run on either system:

    import txaio
    txaio.use_twisted()  # or .use_asyncio()

    f0 = txaio.create_future()
    f1 = txaio.as_future(some_func, 1, 2, key='word')
    txaio.add_callbacks(f0, callback, errback)
    txaio.add_callbacks(f1, callback, errback)
    # ...
    txaio.resolve(f0, "value")
    txaio.reject(f1, RuntimeError("it failed"))

Please refer to the documentation for description and usage of the library features.