Talin wrote:

However, to address the OP's question, do this instead: foo = \ Foo(x=1, y=2)( Foo(x=4, y=5)( Foo(x=3,y=4)(), Foo(x=5,y=6)()) ) )

I use this form in my real coding.

Georg Brandl wrote:

However, exchanging poisitional and keyword arguments is not in the scope of the PEP, and isn't likely to have any future at all -- it's just too ambiguous when the called object has named arguments instead of a catch-all *args in its signature.

More precisely I asked about the following thing.

Let

def foo(*args, **kw): ...

So

in call: foo(x=2,y=3, a,b,c) args = [a,b,c] and kw = {'x':2, 'y':3}

in call: foo(a,b,c, x=2, y=3) args = [a,b,c] and kw = {'x':2, 'y':3} too.

It's just simmetrical form of calling syntax.

Best regards, Zaur