On Fri, Mar 27, 2009 at 1:06 AM, Greg Ewing <greg.ew...@canterbury.ac.nz> wrote: > P.J. Eby wrote: > >> Could we at least have some syntax like 'return from yield with 43', to >> distinguish it from a regular return, clarify that it's returning a value to >> a yield-from statement, and emphasize that you need a yield-from to call it? > > You don't, though -- yield-from just happens to be a particularly > convenient way. > > I suppose what you really mean is that you can't just use an > ordinary call. But generators already have that property, > whether they return values or not, and they're already > syntactically marked as such by containing 'yield'. I don't > see that we need a second syntactic marker.
Because for vanilla generators a return is always a mistake. >> If it doesn't have some sort of variant syntax, the error message for the >> return exception is going to need to be rather verbose > > If we're going to treat this as an error at all, I imagine > it would say something like "Return value from generator not > used." RTM to sort out the details. That would be fine with me. >> One remaining quirk or missing piece: ISTM there needs to be a way to >> extract the return value without using a yield-from statement. > > I did suggest a for-loop variant for doing this, but Guido warned > me not to complicate the PEP any further, so I haven't. A followup > PEP for it might be in order. I don't think this is a requirement, though I expect there will be a way since the error will result into some kind of exception, which means you'll be able to catch it by explicitly invoking __next__(). (BTW, at the language summit we reached the conclusion that proposed language changes need to be aimed at Py3k first (3.1 in this case) and backported to 2.x -- 2.7 in this case. You might want to tweak the proposal to apply to 3.x by default.) -- --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
