Proxy object in Python

A somewhat elegant solution is by creating an “attribute proxy” on the wrapper class:

class Wrapper(object):
    def __init__(self, wrappee):
        self.wrappee = wrappee

    def foo(self):
        print 'foo'

    def __getattr__(self, attr):
        return getattr(self.wrappee, attr)


class Wrappee(object):
    def bar(self):
        print 'bar'

o2 = Wrappee()
o1 = Wrapper(o2)

o1.foo()
o1.bar()

all the magic happens on the __getattr__ method of the Wrapper class, which will try to access the method or attribute on the Wrapper instance, and if it doesn’t exist, it will try on the wrapped one.

if you try to access an attribute that doesn’t exist on either classes, you will get this:

o2.not_valid
Traceback (most recent call last):
  File "so.py", line 26, in <module>
    o2.not_valid
  File "so.py", line 15, in __getattr__
    raise e
AttributeError: 'Wrappee' object has no attribute 'not_valid'