On Oct 1, 9:46 am, Luis Zarrabeitia <[EMAIL PROTECTED]> wrote: > 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
It wouldn't be that hard to make your own. a = peekingiter([1,2,3,4,5]) b = peekingiter([1,2,3]) Just don't cross it with typing and get peking duck. -- http://mail.python.org/mailman/listinfo/python-list
