Thank you for bringing that to my attention!

I think maybe can the interpreter decide whether __class__ etc. should be added to the environment with regard to how the function is called?

The interpreter does not provide __class__ etc. for plain placement() calls, but provide them at calls like child().foo() - when the callee function is named as a class method. Dynamically.

#2/3

Also thanks for the idea of super(type(self), self) - that works! Like this,

class base():
    def foo(self) -> None:
        print('Base!')

def placement(self) -> None:
    super(type(self), self).foo()
       
class child(base):
    def foo(self) -> None:
        pass
    foo = placement
   
child().foo()

But in a more complex case where the base class calls also calls super() this way, it runs into an infinite recursion. Like:

class base():
    def foo(self) -> None:
        print('Base!')

def placement(self) -> None:
    super(type(self), self).foo()
        
class child(base):
    def foo(self) -> None:
        pass
    foo = placement

class child2(child):
    def foo(self) -> None:
        pass
    foo = placement
    
child2().foo()

#3/3

I also found it interesting that there are different results from rebinding a class method with a function defined outside the class, and with a function defined inside the class. Version 1 and version 2 results in the same error message:

class base:
    def foo(self) -> None:
        print('Base!')

class child(base):
    def foo(self) -> None:
        super().foo()

class another(base):
    foo = child.foo

another().foo()

Version 2:

class base:
    def foo(self) -> None:
        print('Base!')

class child(base):
    def foo(self) -> None:
        print('Child!')
    def placement(self) -> None:
        super().foo()
    foo = placement

class another(base):
    foo = child.foo

another().foo()

which all result in a mysterious

TypeError: super(type, obj): obj must be an instance or subtype of type

I guess there is an argument issue. Maybe foo() is called as a classmethod?

While this,

class base:
    def foo(self) -> None:
        print('Base!')

def placement(self) -> None:
    super().foo()
       
class child(base):
    def foo(self) -> None:
        print('Child!')
    foo = placement

class another(base):
    foo = child.foo

another().foo()

Results in the familiar RuntimeError: super(): __class__ cell not found.

Thank you!

Yua

How would the interpreter know which 

Class the rebound “belonged” to? 

For example, that same function could be added to two different classes— then what would super() do? 

BTW, the Python 2 style of calling súper with the class and instance as arguments might work in the case :-)

As an experiment, try adding the placement method to a different class altogether and see what you get.

class another:

    foo = child.placement

-CHB

On Tue, Jul 27, 2021 at 8:16 PM Yua <uncha21@163.com> wrote:

For example, the following code would report an error:

    class base():
         def foo(self) -> None:
             print('Base!')

    def placement(self) -> None:
         super().foo()

    class child(base):
         def foo(self) -> None:
             pass
         foo = placement

    child().foo()

RuntimeError: super(): __class__ cell not found


However, it would be OK if `placement` is defined inside the class:

    class base():
         def foo(self) -> None:
             print('Base!')

    class child(base):
         def placement(self) -> None:
             super().foo()
         def foo(self) -> None:
             pass
         foo = placement

    child().foo()

which prints:

    Base!


I think it would be natural if those functions that was defined outside
a class, but then rebound into a class, can see magic variables like
__class__ that are only shared by those functions defined inside a class.


Thank you!


_______________________________________________
Python-ideas mailing list -- python-ideas@python.org
To unsubscribe send an email to python-ideas-leave@python.org
https://mail.python.org/mailman3/lists/python-ideas.python.org/
Message archived at https://mail.python.org/archives/list/python-ideas@python.org/message/GTTD2CSWNCSH2UW657YK3M7GPSUOKWYS/
Code of Conduct: http://python.org/psf/codeofconduct/

--

Christopher Barker, PhD (Chris)

Python Language Consulting
  - Teaching
  - Scientific Software Development
  - Desktop GUI and Web Development
  - wxPython, numpy, scipy, Cython