Intercept python instance

intercept_instance.py

# In Groovy we can add interception to an instance (not to a whole class) by means of adding it to the instance metaclass
# we can do something like that in Python by creating a new class that inherits the original class of the instance, and changing the class of the instance
# in that new class we implement __getattribute__

class Person:
    def __init__(self, name):
        self.name = name

    def say_hi(self, person):
        #print("inside say_hi")
        return f"Hi person, I'm {self.name}"


def add_interception_to_instance(obj, interceptor_fn):
    class Interceptor_class(obj.__class__):
        def __getattribute__(self, name):
            interceptor_fn(self, name)
            return object.__getattribute__(self, name)
    obj.__class__ = Interceptor_class

p1 = Person("Xuan")
print(p1.say_hi("Francois"))
# Hi person, I'm Xuan

def logger_interceptor_fn(obj, attr):
    print(f"intercepting access to {attr}")

add_interception_to_instance(p1, logger_interceptor_fn)
print(p1.say_hi("Francois"))
#interception happens:
# intercepting access to say_hi
# intercepting access to name
# Hi person, I'm Xuan
print(isinstance(p1, Person))
# True

# other instances of Person are not intercepted
p2 = Person("Iyan")
print(p2.say_hi("Francois"))
# Hi person, I'm Iyan