On Thu, Nov 14, 2013 at 9:58 AM, Andrew Barnert email@example.com wrote:
sub5 = partial(sub, ..., 5)
(At the expense of giving up the abitily to pass ellipsis to partial functions).
I don't know why, but to me that strongly implies that I'm binding argument -1 (after 0 or more arguments, or maybe 1 or more), rather than argument 2 (after exactly 1).
But that's not necessarily a bad thing. But if other people expect it to bind 2, they'll be surprised when they try it on a 3-argument (or variable-argument) function.
(And yes, I realize that mixing 1-based arg counting with python negative indices is potentially confusing. I don't think it's confusing in this particular case, but in, say, documentation for a stdlib function it could be.)0
from functools import partial, __
sub5 = partial(sub, __, 5) xyz = partial(x, __, y, __, z)
(Not quote sure what number of _ would work.) Then you could use ... to do the -1 argument binding:
xyz = partial(x, __, y, ..., z)
Incidentally, since partial(x) doesn't do anything useful (why does it not raise an exception?) would the following ever be reasonable to support?
sub5 = partial(sub)(__, 5)
The advantage is that the signature of the partial function stands alone making it easier to read. That is,
def new_partial(func, args, **kwargs): if not args and not kwargs: return partial(partial, func) return partial(func, args, **kwargs)
Probably the status quo wins.