"Heiko Wundram" <[EMAIL PROTECTED]> wrote in message news:[EMAIL PROTECTED] > > On Sunday 20 March 2005 20:47, George Sakkis wrote: > > Not always. Say for example that you're doing some 2D geometry stuff, and > > later you have to extend it to 3D. In this case you may have to deal with > > both 2D and 3D objects, and map the former to the latter when necessary. > > But this rather sounds like you'd want an adaptor iterator, like the > following: > > >>> class AdaptPossible2D(object): > ... def __init__(self,data): > ... self.data = data > ... def __iter__(self): > ... for item in self.data: > ... if len(item) == 2: > ... yield item+(0,) > ... else: > ... yield item > ... > >>> for x,y,z in AdaptPossible2D([(1,2),(1,2,3),(3,4)]): > ... print x,y,z > ... > 1 2 0 > 1 2 3 > 3 4 0 > > Using the above code makes it absolutely clear what you want, and doesn't need > any new syntax which can be ambiguous like (x=0,y,z=0), etc. The above idiom > also takes only constant extra space, as it doesn't duplicate the list during > iteration.
Once more, the 2D/3D example was just that, an example; my point was not to find a specific solution to a specific problem. Extending the "for .. in" syntax would be an elegant way to express this idea in a more succint, familiar and generic way than a customized adaptor. As for the ambiguity, it is not more ambiguous than function signatures as long as all keyword arguments go after all the required ones; I'm not suggesting that (x=0,y,z=0) should be valid. George -- http://mail.python.org/mailman/listinfo/python-list
