On 4/25/06, Phillip J. Eby <[EMAIL PROTECTED]> wrote: > At 04:18 PM 4/25/2006 -0700, Guido van Rossum wrote: > >But the question remains, > >under what circumstances is it convenient to call __context__() > >explicit, and pass the result to a with-statement? > > Oh. I don't know of any; I previously asked the same question myself. I > just eventually answered myself with "I don't care; we need to require > self-returning __context__ on execution context objects so that the > documentation can appear vaguely sane." :) > > So, I don't know of any non-self-returning use cases for __context__ on an > object that has __enter__ and __exit__. In fact, I suspect that we could > strengthen the requirements to say that: > > 1. If you have __enter__ and __exit__, you MUST have a self-returning > __context__ > > 2. If you don't have __enter__ and __exit__, you MUST NOT have a > self-returning __context__ > > #2 is obvious since you can't use the object with "with" otherwise. #1 > reflects the fact that it doesn't make any sense to take the context of a > context.
I would augment #1 to clarify that if you have __enter__ and __exit__ you may not have __context__ at all; if you have all three, __context__ must return self. #2 is unnecessary (already covered elsewhere). -- --Guido van Rossum (home page: http://www.python.org/~guido/) _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
