On Thu, Nov 14, 2013 at 9:58 AM, Andrew Barnert <abarnert@yahoo.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

How about:

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.

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