Py-duet

Simple future-based async library for python

Duet takes inspiration from the amazing trio library and the structured concurrency approach to async programming that it uses. However, duet differs from trio in two major ways

• Instead of a full-blown implementation of asynchronous IO, duet relies on the Future interface for parallelism, and provides a way to run async/await coroutines around those Futures. This is useful if you are using an API that returns futures, such as RPC libraries like gRPC. The standard Future interface does not implement await directly, so Future instances must be wrapped in duet.AwaitableFuture.

• duet is re-entrant. At the top level, you run async code by calling duet.runfoo. Inside foo suppose you call a function that has not yet been fully refactored to be asynchronous, but itself calls duet.runbar. Most async libraries, including trio and asyncio, will raise an exception if you try to “re-enter” the event loop in this way, but duet allows it. We have found that this can simplify the process of refactoring code to be asynchronous because you don’t have to completely separate the sync and async parts of your codebase all at once.