Question

 class Method(object):
     def __call__(self):
         #how could I get the App instance here?
         return True

 class App(object):
     def __init__(self):
         self.g = Method()

As you can see, the above code can explain my question.

Answer 1

You’d have to store a pointer back to the App object in the Method:

class Method(object):
    def __init__(self, app):
        self.app = app

    def __call__(self):
        self.app.something()
        return True

class App(object):
    def __init__(self):
        self.g = Method(self)

If you have an absolute need to avoid passing the self pointer in App, you’ll need to inspect the stack to retrieve it instead.

The following is discouraged and only works when you instantiate Method objects in a method of App:

import sys

class Method(object):
    def __init__(self):
        parent = sys._getframe(1) # Calling context
        locals_ = frame.f_locals
        assert ('self' in locals_,
            'Method objects can only be instanciated inside instance methods')
        self.app = locals_['self']