If you give my second patch an LGTM I'll submit it and you're done. On Mon, Jul 30, 2012 at 9:58 AM, Alex Gaynor <alex.gay...@gmail.com> wrote: > > > On Mon, Jul 30, 2012 at 9:51 AM, Guido van Rossum <gu...@python.org> wrote: >> >> Also, I have a few content quibbles: >> >> - Is it really worth flagging a negative return value with ValueError? >> I'd just as well clip this to zero. What's the worry? That the >> computed value is wrong? But it's only meant to be a hint, and why >> would -1 be any more wrong than e.g. 1000000000? >> > > This was done for consistency with len(), I'm not particularly attached to > any behavior. > >> >> - Did you mean to define operator.length_hint()? >> > > Of course :) > >> >> - The default can be zero with no semantic impact, so I think there's >> no need to require the caller to specify a default. >> > > I suppose that's fair. > >> >> - Most importantly: calling len(obj) and catching TypeError can only >> be a substitute for the real implementation, which IMO ought to check >> for the presence of a tp_len slot. Alas, checking hasattr(obj, >> '__len__') doesn't quite cut it either, since this returns true for a >> class object that defines a __len__ method for its instances (the >> class itself doesn't have a length). Still, I worry that calling >> len(obj) and catching all TypeErrors overspecifies the desired >> behavior; what I *want* to happen is to check if there is a __len__ >> method, and if so, call it and let any exceptions bubble through. It >> may be best to add a comment explaining that am implementation doesn't >> have to follow the letter of the Python code in the PEP, in >> particular, if obj *has* a __len__() method but calling it raises an >> exception, then length_hint(obj) may (ought to?) pass this exception >> on instead of calling obj.__length_hint__(). >> > > Seems reasonable, rather than try to spec that out precisely in the > pseudocode (aka Python ;)) a note like you suggest sounds good. > >> >> -- >> --Guido van Rossum (python.org/~guido) > > > > Alex > > -- > "I disapprove of what you say, but I will defend to the death your right to > say it." -- Evelyn Beatrice Hall (summarizing Voltaire) > "The people's good is the highest law." -- Cicero >
-- --Guido van Rossum (python.org/~guido) _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
