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
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
type.__getattribute__, but at least in the reference C implementation, type is implemented in C and there is nothing exposed where you could set such a breakpoint with pdb.
type.__getattribute__. Seems like a rare use case.
__getattribute__ return in Foo? I tried the same structure as above, but changed to simply return 42 in MyMeta.__getattribute__. However if I call Foo.age I still get 18, not 42.return super().__getattribute__(name) with return 42? In that case Foo.age should return 42 and it works for me.
__dict__isn't a method; the instance dict is directly available with this name, you don't call it.__dict__is a descriptor which provides the instance dict.__dict__is also a magic method.