[Python-Dev] PEP 342 suggestion: start(), call() and unwind_call() methods (original) (raw)

Guido van Rossum guido at python.org
Sat Oct 8 23:29:21 CEST 2005

On 10/7/05, Piet Delport <pjd at satori.za.net> wrote:

Earlier this week, i proposed legalizing "return Result" inside a generator, and making it act like "raise StopIteration( Result )", for exactly this reason.

IMHO, this is an elegant and straightforward extension of the current semantics of returns inside generators, and is the final step toward making generator-based concurrent tasks[1] look just like the equivalent synchronous code (with the only difference, more-or-less, being the need for appropriate "yield" keywords, and a task runner/scheduler loop). This change would make a huge difference to the practical usability of these generator-based tasks. I think they're much less likely to catch on if you have to write "raise StopIteration( Result )" (or "return( Result )") all the time. [1] a.k.a. coroutines, which i don't think is an accurate name, anymore.

Before we do this I'd like to see you show some programming examples that show how this would be used. I'm having a hard time understanding where you would need this but I realize I haven't used this paradigm enough to have a good feel for it, so I'm open for examples.

At least this makes more sense than mapping "return X" into "yield X; return" as someone previously proposed. :)

-- --Guido van Rossum (home page: http://www.python.org/~guido/)

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