[Delaney, Timothy] > PEP 340 does not address "normal" iterators very well, but a > properly-constructed iterator will behave correctly.
This is by design. > The PEP though is very generator-focussed. Disagree. The PEP describes most everything (e.g. the block statement semantics) in terms of iterators, and then describes how the new APIs behave for generators. > The issues I see for "normal" > iterators (and that need to be addressed/stated in the PEP) are: > > 1. No automatic handling of parameters passed to __next__ and __exit__. > In a generator, these will raise at the yield-statement or -expression. > A "normal" iterator will have to take care of this manually. Not sure what you mean by this. If __next__() is defined, it is passed the parameter; if only next() is defined, a parameter (except None) is an error. That seems exactly right. Also, if __exit__() isn't defined, the exception is raised, which is a very sensible default behavior (and also what will happen to a generator that doesn't catch the exception). > This could be an argument to only allow generator-iterators to be used > with PEP 340 semantics (i.e. continue <EXPR>, block), but I don't think > it's a very compelling one. Neither do I. :-) > Although perhaps the initial implementation could be restricted to > generator-iterators. So if a for-loop used `continue <EXPR>` it would > have a check (at the start of the for loop) that the iterator is a > generator-iterator. Likewise, a block-statement would always include > this check. But what would this buy you except an arbitrary restriction? > As another option, it might be worthwhile creating a base iterator type > with "correct" semantics. Well, what would the "correct" semantics be? What would passing a parameter to a list iterator's __next__() method mean? -- --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
