# txaio: Twisted/asyncio helper

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

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.

Support: either asyncio or Twisted on any of Python 2.7, 3.4 and PyPy.

## How txaio 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:

    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"))

See Restrictions and Caveats for limitations.

- txaio Overview
  - Brief History
  - Overview by Example
  - Restrictions and Caveats
  - Futures and Deferreds
  - Callbacks and Errbacks
  - Real Examples
  - Cross-API Magic
- txaio API
  - Explicitly Selecting a Framework
  - Set an Event Loop / Reactor
  - Test Helpers
  - txaio module