Write async. Get sync for free.

When you write a Python library, you have a dilemma. Ship async-only? Ship blocking-only? Or write everything twice and watch both copies drift?

Synchronicity removes this dilemma. Write your library once (in async) and get a blocking interface for free, while avoiding the boilerplate and limitations of asyncio.run() wrappers. We’ll talk through how to handle persistent connections, async generators, clean tracebacks, type hints and more.

We've used it in production at Modal for years, and it's fully open source. We hope it can save you from writing your own library twice!