Whoa, folks! Can I ask the gentlemen to curb their enthusiasm? PEP 343 is still (back) on the drawing table, PEP 342 has barely been implemented (did it survive the AST-branch merge?), and already you are talking about adding more stuff. Please put on the brakes!
If there's anything this discussion shows me, it's that implicit contexts are a dangerous concept, and should be treated with much skepticism. I would recommend that if you find yourself needing context data while programming an asynchronous application using generator trampolines simulating coroutines, you ought to refactor the app so that the context is explicitly passed along rather than grabbed implicitly. Zope doesn't *require* you to get the context from a thread-local, and I presume that SQLObject also has a way to explicitly use a specific connection (I'm assuming cursors and similar data structures have an explicit reference to the connection used to create them). Heck, even Decimal allows you to invoke every operation as a method on a decimal.Context object! I'd rather not tie implicit contexts to the with statement, conceptually. Most uses of the with-statement are purely local (e.g. "with open(fn) as f"), or don't apply to coroutines (e.g. "with my_lock"). I'd say that "with redirect_stdout(f)" also doesn't apply -- we already know it doesn't work in threaded applications, and that restriction is easily and logically extended to coroutines. If you're writing a trampoline for an app that needs to modify decimal contexts, the decimal module already provides the APIs for explicitly saving and restoring contexts. I know that somewhere in the proto-PEP Phillip argues that the context API needs to be made a part of the standard library so that his trampoline can efficiently swap implicit contexts required by arbitrary standard and third-party library code. My response to that is that library code (whether standard or third-party) should not depend on implicit context unless it assumes it can assume complete control over the application. (That rules out pretty much everything except Zope, which is fine with me. :-) Also, Nick wants the name 'context' for PEP-343 style context managers. I think it's overloading too much to use the same word for per-thread or per-coroutine context. -- --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
