Am 09.10.2013 16:53, schrieb Larry Hastings: > On 10/09/2013 04:26 PM, Georg Brandl wrote: >>> I realize you are -1 on the proposal in general, but I'd be very interested >>> if >>> you could propose an alternate approach where I didn't need "a new spelling >>> for >>> None" as you put it. >> I think I would make Steven's proposed syntax mandatory: let the implementor >> of the function decide which value stands for "not given" -- just like we do >> in the C version, BTW. > > But that's not how addch works. addch counts how many arguments it received; > if > it is called with one or two, it does one thing, and if it's called with three > or four it does something else. You can't duplicate these semantics with
Well, why should a function that requires counting arguments even in C code not be implemented using *args? Documentation can cope fine, in the case of range() with two signatures. > Similarly, you can't accurately express the semantics of range's arguments > using > default values. PyPy's approach is approximately like this: > > def range(x, y=None, step=None): > step = 1 if step is None else step > if y is not None: > start, stop = x, y > else: > start, stop = 0, x > > But now introspection information on range() is inaccurate and unhelpful. > (Not > to mention, they allow specifying step without specifying y, by using keyword > arguments.) > > My goal in writing the PEP was to codify existing practice, which meant > reflecting these (annoying!) corner cases accurately. These are only two, one of them being exceedingly obscure. The hobgoblin comes to mind :) cheers, Georg _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
