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On Sat, Mar 15, 2014 at 4:02 AM, Giampaolo Rodola' <g.rodola@gmail.com> wrote:
On Sat, Mar 15, 2014 at 3:17 AM, Guido van Rossum <guido@python.org> wrote:
I don't think so. asyncio depends on selectors but not vice versa. The selectors module was not part of PEP 3156\. It is solid and I don't see any reason why it should get a reprieve from the usual strict backwards compatibility standards.One part which can be improved is that right now the selectors module doesn't take advance of e/poll()'s modify() method: instead it just unregister() and register() the fd every time, which is�of course considerably slower (there's also a TODO in the code about this).�I guess that can be fixed later in a safely manner.
Yes, it doesn't change the API so doesn't require provisional status.
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Another concern I have is that we should probably rename self.\_epoll, self.\_select, self.\_kqueue to just "self.\_poller": that would make subclassing easier (see patch in issue http://bugs.python.org/issue18931) and would provide a unified interface for those users who want to reference the underlying poller object for some reason.
Oh, but I don't want to make subclassing easier! And I don't want to open up backdoors for "advanced" users. Plus, the object they'd get is different enough that they should probably know what kind of object it is. If there's a missing API on the selector, we should add that, not tell people to help themselves. There lies madness (like the monkey-patching of asyncore in the past).
The only people subclassing the Selector clases should be people proposing changes to the stdlib. Otherwise, if someone wants to write a Selector-like class for a new platform as a 3rd party class, they should write it from scratch (even using copy/paste!) rather than making a subclass of one of the existing stdlib classes, because otherwise they would (perhaps unintentionally) constrained future evolution of the latter (like the optimization you proposed above).
This downside of using subclassing as an API should be well known by now and widely warned against.