tl; dr *Maybe* staticmethod could be modified to become callable? io.open is a built-in function (type "builtin_function_or_method"). It behaves differently than _pyio.open which is a Python function (type "function"). The difference is in the LOAD_METHOD bytecode which uses __get__() descriptor if available. Built-in function has no __get__() method and so the function is used directly as a method. Python function has a __get__() descriptor which returns the function unchanged when a class method is requested, and create a bound method if an instance method is requested: --- def func(): ... FunctionType = type(func) class MyClass: method = func class_method = MyClass.method assert class_method is func assert class_method is FunctionType.__get__(func, None, MyClass) obj = MyClass() instance_method = obj.method assert instance_method.__self__ is obj assert instance_method.__func__ is func # each __get__() call creates a new bound method assert instance_method == FunctionType.__get__(func, obj, type(obj)) --- @staticmethod decorator avoids the creation of the bound method: --- def func(): ... class MyClass: method = staticmethod(func) # method = MyClass.method attr = MyClass.__dict__['method'] method = type(attr).__get__(attr, None, MyClass) assert method is func --- The drawback is that the object created by staticmethod cannot be called :-( The following code raises a TypeError: --- wrapped = staticmethod(func) wrapped() --- *Maybe* staticmethod could be modified to become callable? Victor On Wed, Mar 31, 2021 at 2:34 PM Victor Stinner <vstinner@python.org> wrote:

Hi,

The io module provides an open() function. It also provides an OpenWrapper which only exists to be able to store open as a method (class or instance method). In the _pyio module, pure Python implementation of the io module, OpenWrapper is implemented as:

class OpenWrapper: """Wrapper for builtins.open

Trick so that open won't become a bound method when stored as a class variable (as dbm.dumb does).

See initstdio() in Python/pylifecycle.c. """ def __new__(cls, *args, **kwargs): return open(*args, **kwargs)

I would like to remove this class which is causing troubles in the PEP 597 implementation, but I don't know how. Simplified problem: --- def func(): print("my func")

class MyClass: method = func

func() # A MyClass.method() # B obj = MyClass() obj.method() # C ---

With this syntax, A and B work, but C fails with TypeError: func() takes 0 positional arguments but 1 was given.

If I decorate func() with @staticmethod, B and C work, but A fails with TypeError: 'staticmethod' object is not callable.

Is OpenWrapper the only way to have a callable object which works in the 3 variants A, B and C?

A, B and C work if MyClass is modified to use staticmethod:

class MyClass: method = staticmethod(func)

Victor -- Night gathers, and now my watch begins. It shall not end until my death.

-- Night gathers, and now my watch begins. It shall not end until my death.

On 3/31/21 6:49 AM, Victor Stinner wrote:

tl; dr *Maybe* staticmethod could be modified to become callable?

There have been other requests to make staticmethod callable, one of them being https://bugs.python.org/issue20309 +1 for having it done. -- ~Ethan~

Honestly it has always bugged me that staticmethod only becomes callable through __get__. So I think this would be fine. But I don't know if there might be unintended consequences.

Do we need _pyio at all? Does PyPy or any other Python implementation use it? On Wed, Mar 31, 2021 at 9:36 PM Victor Stinner <vstinner@python.org> wrote:

Hi,

The io module provides an open() function. It also provides an OpenWrapper which only exists to be able to store open as a method (class or instance method). In the _pyio module, pure Python implementation of the io module, OpenWrapper is implemented as:

class OpenWrapper: """Wrapper for builtins.open

Trick so that open won't become a bound method when stored as a class variable (as dbm.dumb does).

See initstdio() in Python/pylifecycle.c. """ def __new__(cls, *args, **kwargs): return open(*args, **kwargs)

I would like to remove this class which is causing troubles in the PEP 597 implementation, but I don't know how. Simplified problem: --- def func(): print("my func")

class MyClass: method = func

func() # A MyClass.method() # B obj = MyClass() obj.method() # C ---

With this syntax, A and B work, but C fails with TypeError: func() takes 0 positional arguments but 1 was given.

If I decorate func() with @staticmethod, B and C work, but A fails with TypeError: 'staticmethod' object is not callable.

Is OpenWrapper the only way to have a callable object which works in the 3 variants A, B and C?

A, B and C work if MyClass is modified to use staticmethod:

class MyClass: method = staticmethod(func)

Victor -- Night gathers, and now my watch begins. It shall not end until my death. _______________________________________________ Python-Dev mailing list -- python-dev@python.org To unsubscribe send an email to python-dev-leave@python.org https://mail.python.org/mailman3/lists/python-dev.python.org/ Message archived at https://mail.python.org/archives/list/python-dev@python.org/message/QZ7SFW3I... Code of Conduct: http://python.org/psf/codeofconduct/

-- Inada Naoki <songofacandy@gmail.com>

On Thu, Apr 1, 2021 at 11:52 AM Brett Cannon <brett@python.org> wrote:

On Wed., Mar. 31, 2021, 18:56 Inada Naoki, <songofacandy@gmail.com> wrote:

...

Do we need _pyio at all? Does PyPy or any other Python implementation use it?

https://www.python.org/dev/peps/pep-0399/ would suggest rolling back Python support is something to avoid.

Thank you. If we obey PEP 399, we need an easy way to keep consistency between Python function and C function. -- Inada Naoki <songofacandy@gmail.com>