[sorry, forgot the code] Hello,
Below 6 working way to implement __iter__ for a container here simulated with a plain inner list. Sure, the example is a bit artificial ;-) 1. __iter__ returns a generator _expression_ 2. __iter__ *is* a generator 3. __iter__ returns a generator (this one is a bit weird, i guess) 4. __iter__ returns self, its own iterator via next() 5. __iter__ returns an external iterator object 6. __iter__ returns iter() of a collection built just on time (this one is really contrived) Also, one can always traverse the collection (already existing or built then) itself if it not quasi-infinite (no __iter__ at all). "There should be one-- and preferably only one --obvious way to do it" http://www.python.org/dev/peps/pep-0020/ I understand some ways fit given use cases better -- or worse. But it's difficult to find the best one, or even a proper one in a given case. Also, generation and iteration are rather abstract notions. And it's too much variety for me. I am lost in this field. I would enjoy a commented and examplified overview. Denis ----- class Seq(object): def __init__(self, *items): self.items = list(items) def next(self): if self.i < len(self.items): x = pair(self.items[self.i]) self.i += 1 return x raise StopIteration def pairs(l): for n in l.items: yield pair(n) raise StopIteration def __iter__(self): return (pair(n) for n in self.items) def __iter__(self): for n in self.items: yield pair(n) raise StopIteration def __iter__(self): return self.pairs() def __iter__(self): self.i=0 return self def __iter__(self): return Iter(self) def __iter__(self): return iter(tuple([pair(n) for n in self.items])) def pair(n): return "%s:%s" %(n,chr(n+96)) class Iter(object): def __init__(self, l): self.i=0 self.items = l.items def __iter__(self): return self def next(self): if self.i < len(self.items): x = pair(self.items[self.i]) self.i += 1 return x raise StopIteration l = Seq(1,2,3) for x in l: print x, # ==> 1:a 2:b 3:c ________________________________ la vita e estrany spir.wikidot.com _______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
