On Tue, Jun 22, 2021 at 09:12:53PM +1000, Chris Angelico wrote:
> > The must be no semantic difference between:
> >
> > obj.method(arg)
> >
> > and
> >
> > getattr(obj, 'method')(arg)
> >
> > regardless of whether `method` is a regular method or an extension
> > method.
>
> And this is a problem.
If its a problem for getattr, it is a problem for dot syntax, because
they are essentially the same thing.
> How is getattr defined?
The same as it is defined now, except with some minor tweaks to support
extension methods.
Do you remember when we introduced `__slots__` (version 2.2 or 2.3, I
think?), and added a whole new mechanism to look up ordinary attributes
and slot attributes? No, neither do I, because we didn't.
We have a single mechanism for looking up attributes, including methods,
which works with instances and classes, descriptors and non-descripters,
C-level slots and Python `__slots__` and `__dicts__` and `__getattr__`
and `__getattribute__`, and I am absolutely positively sure that if
Python ever adds a new implementation for attribute lookup, it will
still be handled by the same getattr mechanism, which is built into the
interpreter.
> Is it counted as being in the current module?
`getattr`? No, that's a builtin. You can shadow it or delete it if you
want, it's just a public API to the underlying functionality built
into the interpreter. Dot syntax won't be affected.
> If it is, then has getattr magically become
> part of the module it's called from? Or do ALL lookups depend on where
> the function was called, rather than where it's defined?
Can you be a bit more precise? I'm not suggesting that we introduce
dynamic scoping instead of lexical scoping, if that's what you mean.
Attribute lookups already depend on the state of the object at the time
the lookup is made. This is just more of the same.
class K:
pass
K.attr # this is an AttributeError
K.attr = 'extension'
K.attr # this is fine
> If 'method' is an extension method, where exactly is it visible?
I believe that TypeScript uses "import" for this, so it would be visible
from anywhere that imports it:
https://putridparrot.com/blog/extension-methods-in-typescript/
--
Steve
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