When do default parameters get their values set?

[Rustom Mody]

On Thursday, December 11, 2014 12:09:10 AM UTC+5:30, rand... at fastmail.us wrote:
> On Tue, Dec 9, 2014, at 21:44, Rustom Mody wrote:
> > Nice example -- thanks.
> > Elaborates the why of this gotcha -- a def(inition) is imperative.
> > From a semantic pov very clean.
> > From an expectation pov always surprising.
> 
> Of course, I used a lambda for this. The equivalent without would be:
> 
> def f():
>     def g(x={}):
>         return x
>     return g

Ok. As I wrote in the "Question on lambdas" thread yesterday
lambdas and defs are equivalent

And going the other way -- no defs only lambdas its this:


>>> f = lambda : (lambda x= {}: x)
>>> f()() is f()()
False
>>> d = f()
>>> d() is d()
True
>>> 


But I have a different question -- can this be demonstrated without the 'is'?
Because to me 'is' -- equivalently id -- is a code-smell and is like
explaining funny behavior by showing the dis -- like 
$ gcc -S ...
-- output.

It can always explain, but indicates that the semantics is not (sufficiently) abstract in this aspect