For a long time when people criticize threads, my feeling has been that (a) they have a point, but (b) threads aren't as hard as they imply because (c) concurrency is always hard, but mostly (d) thread critics need to provide better tools for concurrency. I know how to use threads, and I'm relatively happy with them; I'm quite willing to look at alternatives, but I don't feel I'm being given very good alternatives. Convince me with carrots instead of sticks. An especially poor argument is one that tells me that I'm currently being beaten with a stick, but apparently don't know it. For people who think threads aren't a reasonable option for concurrency in Python: you are simply wrong, lots of people are successfully using threads for concurrency, and arguments to the contrary are simply delusional.

The Twisted people have tried to provide alternative tools, and they certainly put their hearts into it, but I just don't think their style of asynchronous programming is straight-forward enough for the bulk of programmers. It doesn't provide the gradual learning curve that I value in Python (regardless of where I personally am on that learning curve). It certainly looks like Python 2.5 will improve things, but I don't think the style really elucidates the issues of concurrent programming particularly well. Concurrent programming introduces inevitable challenges; a good model guides the programmer, it can't solve the problems on its own.

The other alternative -- multi-process -- in Python is common enough, but feels very ad hoc to me. There aren't good tools for sharing data and communication (or if there are they aren't well enough publicized). Nor are there good tools for handling multiple processes in a cross-platform way. I don't use Windows, but I'm not willing to abandon Windows users by relying on fork. (That doesn't mean we can't use fork, just that we can't only use fork.)

But, it seems that there might be some progress. I came upon this post by Jeremy Jones about concurrency, which led me to this proposal by Shane Hathaway and this Py-Dev thread.

The discussion seems to have stopped, which is too bad. I hope it starts back up again.