 <p>I've used Selector for the last couple years and found it perfectly stable. It's been at 0.8.11 for at least two years now. </p> <p>I would draw two conclusions from that: </p> <ol> <li><p>It could be basically unmaintained. If you find a bug in it or need a new feature, I wouldn't count on being able to get Luke Arno to jump up and fix it in a hurry (not saying he wouldn't, but I'm guessing that Selector isn't his main focus these days). Would you be comfortable maintaining a local fork in that case?</p></li> <li><p>It's pretty much complete. The problem that it's trying to solve is contained in scope. It's a very small library without much code. The bugs have been shaken out and there's really nothing left to do on it. I think this is the main reason it hasn't been updated in a long time. It's basically done.</p></li> </ol> <p>Open source developers, and Python developers in particular, have a long history of being very (probably overly) conservative about marking things as 1.0. The lack of unit tests can be a little off-putting, but again, it's a small library solving a problem with limited scope. The code is short and clear enough to read and convince yourself of its correctness.</p>