On Thu, Jan 13, 2011 at 10:21 AM, Luc Goossens <luc.goossens@cern.ch> wrote: ..
Sorry maybe this was not clear from my mail but I am not so much interested in possible work-arounds but in why this asymmetry exists in the first place.
It looks like you are asking why tuple unpacking syntax does not support all options available to argument passing. Part of it (the variable length unpacking) is the subject of PEP 3132 <http://www.python.org/dev/peps/pep-3132/>, which was approved, but the implementation was postponed due to the moratorium on language changes in effect for 3.2 release. Note that PEP 3132 does not really achieve symmetry with argument passing because it makes (a, *x, b) = .. valid while f(a, *x, b) is not.
I mean is there a reason as to why it is the way it is, or is it just that nobody ever asked for anything else.
No one has ever proposed a design in which tuple unpacking and argument passing is "symmetric". This may very well be impossible.