On Tue, 22 Nov 2005 14:28:56 GMT, "David Isaac" <[EMAIL PROTECTED]> wrote:
> >"Duncan Booth" <[EMAIL PROTECTED]> wrote in message >news:[EMAIL PROTECTED] >> >>> aList = ['a', 1, 'b', 2, 'c', 3] >> >>> it = iter(aList) >> >>> zip(it, it) >> [('a', 1), ('b', 2), ('c', 3)] > >That behavior is currently an accident. >http://sourceforge.net/tracker/?group_id=5470&atid=105470&func=detail&aid=1121416 >Alan Isaac > That says """ ii. The other problem is easier to explain by example. Let it=iter([1,2,3,4]). What is the result of zip(*[it]*2)? The current answer is: [(1,2),(3,4)], but it is impossible to determine this from the docs, which would allow [(1,3),(2,4)] instead (or indeed other possibilities). """ IMO left->right is useful enough to warrant making it defined behaviour, not an accident. Isn't it(),it() well defined for a given iterator? So is the question whether zip will access its referenced input iterators in some peculiar order? Is the order of zip(a,b) accesses to a and b undefined? If, so, IMO it's reasonable to make it defined as if >>> def zip(*args): ... return list(tuple([it.next() for it in its]) ... for its in [[iter(a) for a in args]] ... for _ in iter(lambda:0,1)) ... >>> aList = ['a', 1, 'b', 2, 'c', 3] >>> it = iter(aList) >>> zip(it, it) [('a', 1), ('b', 2), ('c', 3)] >>> it = iter(aList) >>> zip(it, it, it) [('a', 1, 'b'), (2, 'c', 3)] >>> it = iter(aList) >>> zip(it) [('a',), (1,), ('b',), (2,), ('c',), (3,)] >>> zip(range(3), range(4)) [(0, 0), (1, 1), (2, 2)] >>> zip(range(4), range(3)) [ (0, 0), (1, 1), (2, 2)] (I just hacked this out, so maybe it's not bullet-proof, but the point is, I think there's no reason not to define the behaviour of zip to cycle through its arguments in the intuitive way). Regards, Bengt Richter -- http://mail.python.org/mailman/listinfo/python-list
