On 04/23/18 14:04, Jeroen Demeyer wrote:
Hello,
I just saw this PEP. There is a bit of overlap between PEP 573 and PEP
575 since these both change the calling convention for built-in methods.
In particular, PEP 575 also proposes to add a "defining class" member
(for different reasons). In PEP 575, this is added to the PyCFunction
struct itself instead of a separate struct PyCMethod.
The reason you just saw the pep is because it wasn't posted to
python-dev yet, and it wasn't posted yet because we first want to look
for potential conflicts with 573.
(There's no one forking on PEP 573 full-time, so unfortunately it's
progressing slower than I'd like.)
It would be nice to justify whether you really need a new class
(PyCMethod_Type) to support METH_METHOD. It looks strange to me that the
class of some object depends on an implementation detail like whether
METH_METHOD is specified.
The current PEP 573 implies that backwards compatibility concerns would
arise every time that METH_METHOD is added to an existing method. People
have asked questions on PEP 575 about that: it would break code
depending on "types.BuiltinFunctionType" for example. You could instead
just change PyCFunctionObject to add that field (that's what I did in
PEP 575).
For practical reasons, it would be nice to implement PEP 573 and PEP 575
together as they affect the same code (assuming that both PEPs are
accepted of course).
I currently even think PEP 575 can go forward *before* PEP 573. Having
__objclass__ on methods of extension classes does sounds like a more
elegant solution! And for PEP 573 it would mean one less annoying
problem to solve.
Reading PEP 575, I miss an explanation of what __objclass__ *is* -- it
only says the technical restrictions on it. For PEP 575 I found it
pretty important that the reader gets a good mental picture of what it
is, but it's a bit difficult to explain succinctly.
Maybe something like this would help make it clearer in PEP 573?
If set, `__objclass__` is the class that defines the method (which might
be a superclass of `type(self)`). Functionally it's equivalent to the
`__class__` cell [0] in Python code.
[0]
https://docs.python.org/3/reference/datamodel.html#creating-the-class-object
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