What method does Python call when I access an attribute of a class via the class name?

Question

I know accessing the attributes of Foo through an instance will call the __getattribute__() method, but what if I access this attribute directly through the class? If a function is called, I want to set a breakpoint in it so that the breakpoint can be triggered when accessing this property through a class in my project.

I have tried to set breakpoint in magic method __getattribute__(), but nothing hapened.

class Foo:
    age = 18


print(Foo.age)  # I am curious what method is called

Answer 1

Everything in Python is an object and everything has a type that determines the object's behavior. This also holds for class objects. You can check type(Foo):

>>> type(Foo)
<class 'type'>

You can customize the type of a class by providing a custom metaclass. This metaclass is then responsible for attribute access on the class object:

class MyMeta(type):
    def __getattribute__(self, name):
        print(f'__getattribute__({self!r}, {name!r})')
        return super().__getattribute__(name)


class Foo(metaclass=MyMeta):
    age = 18


print(Foo.age)

and the output is:

__getattribute__(<class '__main__.Foo'>, 'age')
18