Intercepting binding?

[Dave Angel]

andrew cooke wrote:
> This is a bit vague, I'm afraid, but is there any way for me to take
> code like:
>
>    a = Foo()
>    beta = Bar()
>
> and somehow attach the string "a" to the Foo instance and "beta" to
> the Bar instance.  At some later point in the program I want to be
> able to look at the Bar instance and say to the user "this was called
> beta in your routine".
>
> The motivation is debugging an embedded domain specific language and
> the solution has to be cross platform for Python 3+ (bonus points for
> Python 2 too).
>
> Obviously I can parse the code, but I was wondering if there was some
> other (no doubt terribly hacky) approach.  Even some idea of what to
> google for would be a help...
>
> Thanks,
> Andrew
>
>   
This comes up periodically in this list, and the answer is always 
something like:  you can't get there from here.  As you have noticed, it 
can't be done in the __init__() of the object, since the symbol it'll be 
bound to doesn't generally exist yet, and even if it does, there's no 
way to know which one it is.

You could write a function that the user could voluntarily call at the 
end of his function, that would find all symbols of a specified kind, 
and store the kind of information you're asking about.  But of course, 
some class instances should not be added to, and some cannot.  So you'd 
need some form of filter to indicate which ones to do.

In the sample below, I'll assume you want to do this for all classes 
derived from Mybase.

(untested):

def label_stuff(symbols):
    for symbol in symbols:
        if  isinstance(symbols[symbol], Mybase):
            symbols[symbol].bind_name = symbol

And the user would simply make a call at the end of each such function, 
like:

def   my_func():
      a = ...
      b = ...
      label_stuff(locals)