[Python-3000] optional argument annotations

[Tony Lownds]

On Nov 26, 2006, at 1:10 PM, Brett Cannon wrote:

> On 11/24/06, Tony Lownds <tony at pagedna.com> wrote:
> > Obviously signature objects would grow support for annotations,  
> but I
> > still need the information to be carried on the code object to
> > incorporate into signature objects.
> >
>
> Signature objects still need a way to know the nested parameters,  
> right?
>
> They already handle them.
>

I see, through the bytecode inspection that inspect.py does.

> How about a co_argnames attribute? eg for
>
> def f((x, y), z): pass
>
> f.func_code.co_argnames would be (('x', 'y'), 'z')
>
> That's fine, but the compiler would need to change if it were to  
> use this.  Plus I am still hoping to make nested parameters  
> disappear in Py3K (I won't be pushing for it any sooner than PyCon,  
> though).
>

Yes, it is the compiler that would implement this. I have it  
implemented as follows.

 >>> def f(a, (b, c), d=1, *e, f, g=1, **h): pass
...
 >>> f.func_code.co_argnames
('a', ('b', 'c'), 'd', '*e', 'f', 'g', '**h')

However since inspect.py doesn't need this and neither does my code,  
I'll drop it.

> I need to implement something like this to properly build
> func_annotations
> inside MAKE_FUNCTION.
>
>
> I don't quite follow.  Don't you already have support in  
> MAKE_FUNCTION when the object is created?
>

The support available is the code object and anything pushed onto the  
stack. Just looking at the code object,
the information is simply not available outside of reverse- 
engineering co_code (as inspect does).
I ended up pushing a tuple of argument names onto the stack.

eg, for

def f((x:1, y))->3: pass

the bytecode is...

   1           0 LOAD_CONST               0 (1)
               3 LOAD_CONST               1 (3)
               6 LOAD_CONST               2 (('x', 'return'))
               9 LOAD_CONST               3 (<code object f at  
0xb7ecd848, file "<str>", line 1>)
              12 EXTENDED_ARG             3
              15 MAKE_FUNCTION        196608
              18 STORE_NAME               0 (f)
              21 LOAD_CONST               4 (None)
              24 RETURN_VALUE

(the argument is so big because I need to pass the # of annotations  
in the argument of MAKE_FUNCTION so
that the stack effect can be easily calculated)

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