post_man.py

class Router:
    def __new__(cls, origin, destination):
        return ['post_office1', 'post_office2', 'post_office3', 'post_office4']


class Package:
    def __init__(self, route):
        self.route = route
        self.trip = self.generate_trip()

    @property
    def origin(self):
        return self.route[0]

    @property
    def destination(self):
        return self.route[-1]

    def generate_trip(self):
        """
                it's converting the routes to  pairs of origin and destination
                [(a,b),(b,c)]
        """
        return list(zip(self.route, self.route[1:] + self.route[:0])).copy()


class PostMan:
    def __init__(self, name):
        self.name = name
        self.package = None

    def get_package(self, package: Package):
        self.package = package

    def deliver(self, package: Package):
        origin, destination = package.trip[0]
        print(f"package delivered from {origin} to {destination} by  {self.name}")
        package.trip.pop(0)


class PostOffice:
    def __init__(self, name, postman: PostMan = None):
        self.name = name
        self.postman = postman

    def get_postman(self):
        return self.postman


if __name__ == '__main__':
    post_office1 = PostOffice("post_office1", PostMan("postman1"))
    post_office2 = PostOffice("post_office2", PostMan("postman2"))
    post_office3 = PostOffice("post_office3", PostMan("postman3"))

    package = Package(route=Router(origin="post_office1", destination="post_office4"))

    post_man1 = post_office1.get_postman()
    post_man1.get_package(package)
    post_man1.deliver(package)

    post_man2 = post_office2.get_postman()
    post_man2.get_package(package)
    post_man2.deliver(package)

    post_man3 = post_office3.get_postman()
    post_man3.get_package(package)
    post_man3.deliver(package)