Example Python GoF proxy

proxy_example.py

from abc import ABC, abstractmethod


class ProxySubject(ABC):
    """
    The interface we will use in our proxy and subject.
    """

    @abstractmethod
    def do_stuff(self, arg):
        pass

    @abstractmethod
    def say_something(self) -> str:
        pass

    def not_abstract(self) -> str:
        return "default"


class Concrete(ProxySubject):
    """
    Base concrete implementstion
    """
    def do_stuff(self, arg):
        print("Concrete doing stuff with", arg)

    def say_something(self) -> str:
        return "hello"


class Proxy(ProxySubject):
    """
    The proxy which proxies any instance of the interface (so proxies can be chained)
    """
    def __init__(self, delegate: ProxySubject):
        self._delegate = delegate

    def do_stuff(self, arg):
        print("here is the proxy calling the delegate for", arg)
        self._delegate.do_stuff(arg)

    def say_something(self) -> str:
        return self._delegate.say_something().upper()

    def not_abstract(self) -> str:
        return self._delegate.not_abstract()[::-1]


if __name__ == "__main__":
    concrete = Concrete()
    proxy = Proxy(concrete)
    proxy.do_stuff("foo")
    print("Calling the proxy:", proxy.say_something())
    print("calling not_abstract:", proxy.not_abstract())

    proxy2 = Proxy(proxy)
    print("calling proxy chain:", proxy2.not_abstract())