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Convert trollius code to asyncio

Project description


A tool based on lib2to3 for converting code using trollius to use asyncio. After installation, run trollius2asyncio. It works in the same way as 2to3.

For example, it will transform this:

import trollius
from trollius import From, Return

def double_future(future):
    value = yield From(future)
    raise Return(2 * value)


import asyncio

async def double_future(future):
    value = await future
    return 2 * value


After installation, run trollius2asyncio as you would 2to3. It takes the same command-line arguments, including -h for help.


It recognises From, trollius.From, Return and trollius.Return, without taking the imports into consideration. Thus, importing trollius as a different name will confuse it, and from tornado.gen import Return will cause the returns from Tornado to also be rewritten (which should still be a legal transformation).

It recognises @trollius.coroutine, again without taking imports into consideration. If the decorator is omitted, it won't turn the function into a coroutine, which will lead to syntax errors if it ends up containing await statements. It also won't apply the transformation if there are additional decorators inside (i.e., between @trollius.coroutine and the definition) since that would alter the semantics.

The resulting code is not necessarily well-styled e.g., the extra blank line in the example above. These are limitations of lib2to3 and won't be easy to fix without risking breaking code in corner cases.

Release history


  • Drop Python 3.4 support (output code uses async and await).


  • Add licence.


  • Initial release.

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