[Python-Dev] PEP: 576 Title: Rationalize Built-in function classes (original) (raw)

Jeroen Demeyer J.Demeyer at UGent.be
Sun May 20 15:26:00 EDT 2018

On 2018-05-19 11:15, mark wrote:

PEP 576 aims to fulfill the same goals as PEP 575

(this is a copy of my comments on GitHub before this PEP was official)

Performance

Most importantly, changing bound methods of extension types from builtin_function_or_method to bound_method will yield a performance loss. It might be possible to mitigate this somewhat by adding specific optimizations for calling bound_method. However, that would add extra complexity and it will probably still be slower than the existing code.

And I would also like to know whether it will be possible for custom built-in function subclasses to implement get to change a function into a method (like Python functions) and whether/how the LOAD_METHOD opcode will work in that case.

Introspection

When I want "introspection support", that goes beyond the call signature. Also inspect.getfile should be supported. Currently, that simply raises an exception for built-in functions.

I think it's important to specify the semantics of inspect.isfunction. Given that you don't mention it, I assume that inspect.isfunction will continue to return True only for Python functions. But that way, these new function classes won't behave like Python functions.

fully backwards compatible.

I wonder why you think it is "fully backwards compatible". Just like PEP 575, you are changing the classes of certain objects. I think it's fairer to say that both PEP 575 and PEP 576 might cause minor backwards compatibility issues. I certainly don't think that PEP 576 is significantly more backwards compatible than PEP 575.

PS: in your PEP, you write "bound_method" but I guess you mean "method". PEP 575 proposes to rename "method" to "bound_method".

Jeroen.

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