[Python-Dev] Python Call Mechanism

[Guido van Rossum]

> Hmm - the interaction of "a=b" style args & *-ed args is a bit
> counter-intuitive, particularly as the "a=b" args syntatically have to
> come before the *-ed args:
> 
> >>> def f(a,b,c,d):
> ...  return a,b,c,d
> ... 
> >>> f(1,c=3,*(2,4))
> Traceback (most recent call last):
>   File "<stdin>", line 1, in ?
> TypeError: keyword parameter 'c' redefined in call to f()
> >>> f(1,b=3,*(2,4))
> Traceback (most recent call last):
>   File "<stdin>", line 1, in ?
> TypeError: keyword parameter 'b' redefined in call to f()
> >>> f(1,d=4,*(2,3))
> (1, 2, 3, 4)
> 
> I humbly submit that This Is Wrong.  I haven't seen anybody complain
> about it, which suggests to me that noone is using this combination,
> and I propose either:
> 
> 1) banning it
> 2) demanding that the *-ed arg precede the "a=b" args

Interesting.  The *-ed arg cannot precede the a=b args currently, but
I agree that it would have made more sense to do it that way.

I'm not sure that it's worth allowing the combination of kw args and
*tuple, but I'l also not sure that it *isn't* worth it.

> Of course, if noone is using this "feature", then maybe this dusty
> little corner of the language should be left undisturbed.

I think it may be best to leave it alone.

> And I haven't even thought about default arguments yet...

That's unrelated.

--Guido van Rossum (home page: http://www.python.org/~guido/)