Whilst reading PEP3107 on what's coming this year in Python 3000 I came across this section where it mentions nested parameters in function definitions.
I could not emember this feature so googled a bit, and still could not find it.
It was time to suck-it-and-see, so using Python2.5 I did:
My current skunk-works project extracts data from VHDL source files as a list of nested tuples. I use each outer tuple as a record but unpack the record manually at each function call. If I used the above then the function parameter definition would reflect the record structure.
>>> def x ((p0, p1), p2):
... return p0,p1,p2
>>> x(('Does', 'this'), 'work')
('Does', 'this', 'work')
On closer inspection of the Python Function definition grammar, I find that nested parameters are represented by the sublist token.