Hi there. For most use cases I think about, the iterator protocol is more than enough. However, on a few cases, I've needed some ugly hacks.
Ex 1: a = iter([1,2,3,4,5]) # assume you got the iterator from a function and b = iter([1,2,3]) # these two are just examples. then, zip(a,b) has a different side effect from zip(b,a) After the excecution, in the first case, iterator a contains just [5], on the second, it contains [4,5]. I think the second one is correct (the 5 was never used, after all). I tried to implement my 'own' zip, but there is no way to know the length of the iterator (obviously), and there is also no way to 'rewind' a value after calling 'next'. Ex 2: Will this iterator yield any value? Like with most iterables, a construct if iterator: # do something would be a very convenient thing to have, instead of wrapping a 'next' call on a try...except and consuming the first item. Ex 3: if any(iterator): # do something ... but the first true value was already consumed and # cannot be reused. "Any" cannot peek inside the iterator without # consuming the value. Instead, i1, i2 = tee(iterator) if any(i1): # do something with i2 Question/Proposal: Has there been any PEP regarding the problem of 'peeking' inside an iterator? Knowing if the iteration will end or not, and/or accessing the next value, without consuming it? Is there any (simple, elegant) way around it? Cheers, -- Luis Zarrabeitia (aka Kyrie) Fac. de Matemática y Computación, UH. http://profesores.matcom.uh.cu/~kyrie -- http://mail.python.org/mailman/listinfo/python-list
