[bdarnell]

I think that Python 3.5 now has a very elegant interface for async programming. I prefer Tornado to the standard library's asyncio, but the new keywords are nice for both packages (disclaimer: I'm the maintainer of Tornado).

The downsides have nothing to do with the design of the language. The problem is that introducing a new concurrency model late in a language's life splits the ecosystem. Most existing packages are synchronous, so if you want to build asynchronous systems you must avoid packages like requests, django, or sqlalchemy and find (or develop) asynchronous equivalents for the functionality you need.

Javascript has an advantage here not because the design of the language is especially well-suited for asynchronous programming, but because it never went through a synchronous/multi-threading phase. Every javascript package is designed for asynchronous use.

[nbadg]

Yeah, my biggest complaint personally is that combining multithreading and async is a massive pain in the ass. Now, realistically, you aren't usually going to want to do that, except if you have multiple event loops, or are bridging between external synchronous code and internal async code. Otherwise, I really enjoy async python -- of course, I'm also the kind of person who has written my own event loops using synchronous code before, so maybe I'm just crazy like that.

[markbnj]

>> The problem is that introducing a new concurrency model late in a language's life splits the ecosystem.

Really you could say that about a number of features/changes in python 3, not just the new async syntax. Python 3 itself was an ecosystem-splitting instrument.