There is probably some existing python API you can hijack to make custom
locals() and globals() work everywhere. Perhaps pdb and inspect.stack are good
places to start; maybe there’s a PDB API to break on every new stack frame and
maybe you can use inspect to do the proper assignment overrides.
Python is a very layered language.
Sent from my iPhone
> On May 25, 2019, at 4:53 AM, Yanghao Hua <yanghao...@gmail.com> wrote:
>
>> On Fri, May 24, 2019 at 10:34 PM Ricky Teachey <ri...@teachey.org> wrote:
>>
>> You can do things like this with exec():
>>
>> class SafeDict(dict):
>> curated_keys = {"a", "b", "c"}
>> def __setitem__(self, k, v):
>> if k not i self.curated_keys:
>> raise Exception(f"{k!r} key not allowed")
>> super().__setitem__(k, v)
>>
>> locals_dict = SafeDict()
>> globals_dict = SafeDict()
>>
>> exec("d=1", locals_dict, globals_dict) # Exception: 'd' key not allowed
>>
>> You can do all sorts of things using that technique, including the way
>> assignment to variables is handled.
>
> I see your point now. In this case user will need to write HDLs
> probably in below fashion:
>
> class my_module:
> def __init__(self, input, output, ...):
> ...
> def process(self):
> exec("signal = 5", locals, globals)
> # compare this with: signal <== 5
>
> I fully agree this can work, but also it doesn't seem to be any better
> looking than signal.next = 5. I think there are two important point
> here, first is to make HDL design feels as natural as possible and as
> pythonic as possible as well as leaving very little room for mistakes,
> second is to make HDL design at least as easy and as intuitive as in
> traditional HDLs. And when I see this can actually be achieved easily
> with less than 100 lines of CPython code changes I am tempted to give
> it a try (I am so in love with python ...).
>
> The other thing I was thinking about is PEP572 assignment expression
> (a := b), if it could be modified to allow user override (e.g. via
> __assign__()), and allow it to be used without bracket like "y :=
> f(x)" if __assign__ is present in y. Then this is even aligned with
> Chisel's assignment operation and I'd be completely happy with it.
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