This discussion probably belongs to python-ideas, but since we already have this thread, I'll reply here instead of opening a new thread there.
Ellipsis was introduced into python to serve needs of the numeric python community. If you think of numpy multiarrays as functions taking ndim number of arguments, then ellipsis is used to denote any number of missing arguments and : is used to denote a single missing argument. By this analogy, partial(f, ..., *args) is right_partial with '...' standing for any number of missing arguments. I you want to specify exactly one missing argument, you would want to write partial(f, :, *args), which is not a valid syntax even in Py3. If one is willing to use [] instead of () with partial, it is possible to implement partial[f, ..., *args] and partial[f, x, :, z] already in Py2, but I would rather see : allowed in the argument lists or some other short syntax for missing arguments. If such syntax is introduced, the need for partial may even go away with partial(str.split, :, ',') spelled simply as str.split(:, ','). On Thu, Jan 29, 2009 at 3:04 PM, Antoine Pitrou <solip...@pitrou.net> wrote: > Scott David Daniels <Scott.Daniels <at> Acm.Org> writes: >> >> Antoine Pitrou wrote: >> > ... >> > In py3k, we could also use "..." (the Ellipsis object) to denote >> > places where an argument is missing, so that: >> > split_comma = partial(str.split, ..., ',') >> > would do what you want. >> >> Thus preventing any use of partial when an argument could be an >> the Ellipsis instance. > > Obviously, it is the drawback :) But Ellipsis is hardly used anywhere, and it > reads good in this very use case. > > > > _______________________________________________ > 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/alexander.belopolsky%40gmail.com > _______________________________________________ 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
