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*What is this pattern about?
The Adapter pattern provides a different interface for a class. We can
think about it as a cable adapter that allows you to charge a phone
somewhere that has outlets in a different shape. Following this idea,
the Adapter pattern is useful to integrate classes that couldn't be
integrated due to their incompatible interfaces.
*What does this example do?
The example has classes that represent entities (Dog, Cat, Human, Car)
that make different noises. The Adapter class provides a different
interface to the original methods that make such noises. So the
original interfaces (e.g., bark and meow) are available under a
different name: make_noise.
*Where is the pattern used practically?
The Grok framework uses adapters to make objects work with a
particular API without modifying the objects themselves:
http://grok.zope.org/doc/current/grok_overview.html#adapters
*References:
http://ginstrom.com/scribbles/2008/11/06/generic-adapter-class-in-python/
https://sourcemaking.com/design_patterns/adapter
http://python-3-patterns-idioms-test.readthedocs.io/en/latest/ChangeInterface.html#adapter
Allows the interface of an existing class to be used as another interface.
from typing import Callable, TypeVar
T = TypeVar("T")
    def __init__(self) -> None:
        self.name = "Dog"
    def bark(self) -> str:
        return "woof!"
    def __init__(self) -> None:
        self.name = "Cat"
    def meow(self) -> str:
        return "meow!"
class Human:
    def __init__(self) -> None:
        self.name = "Human"
    def speak(self) -> str:
        return "'hello'"
    def __init__(self) -> None:
        self.name = "Car"
    def make_noise(self, octane_level: int) -> str:
        return f"vroom{'!' * octane_level}"
class Adapter:
    """Adapts an object by replacing methods.
    dog = Dog()
    dog = Adapter(dog, make_noise=dog.bark)
    def __init__(self, obj: T, **adapted_methods: Callable):
        """We set the adapted methods in the object's dict."""
        self.obj = obj
        self.__dict__.update(adapted_methods)
    def __getattr__(self, attr):
        """All non-adapted calls are passed to the object."""
        return getattr(self.obj, attr)
    def original_dict(self):
        """Print original object dict."""
        return self.obj.__dict__
def main():
    >>> objects = []
    >>> dog = Dog()
    >>> print(dog.__dict__)
    {'name': 'Dog'}
    >>> objects.append(Adapter(dog, make_noise=dog.bark))
    >>> objects[0].__dict__['obj'], objects[0].__dict__['make_noise']
    (<...Dog object at 0x...>, <bound method Dog.bark of <...Dog object at 0x...>>)
    >>> print(objects[0].original_dict())
    {'name': 'Dog'}
    >>> cat = Cat()
    >>> objects.append(Adapter(cat, make_noise=cat.meow))
    >>> human = Human()
    >>> objects.append(Adapter(human, make_noise=human.speak))
    >>> car = Car()
    >>> objects.append(Adapter(car, make_noise=lambda: car.make_noise(3)))
    >>> for obj in objects:
    ...    print("A {0} goes {1}".format(obj.name, obj.make_noise()))
    A Dog goes woof!
    A Cat goes meow!
    A Human goes 'hello'
    A Car goes vroom!!!
if __name__ == "__main__":
    import doctest
    doctest.testmod(optionflags=doctest.ELLIPSIS)

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