extend-me 1.1.0

ExtensibleType

At the begining we should create a metaclass that will automaticaly gether all information about all extensions, and apply this metaclass to class we would like to enable extensions for:

>>> import six  # Used for Python 2/3 compatability
>>> mc = ExtensibleType._("Object")

>>> @six.add_metaclass(mc)
... class Object(object):
...     pass

Not method _ of ExtensibleType. This method is used to create metaclass for specific object. It receives one argument - string that will be used as name of class generated by this metaclass

Next we may define extension for this class. It is very simple. Just subclass previously defined class:

>>> class ObjectExtension(Object):
...     cool_attribute = 1
...     def method1(self):
...         return "Test"

So… at this momet we have base class and extension. And here is that core magic occures. Metaclass that was created at the begining automaticaly collects all subclasses of base class. So it is posible now to create new class that is subclass of all subclasses of base class using multiple inheritance. And metaclass mc will do it for You:

>>> cls = mc.get_class()

And now You can use cls for Your needs, instead of base class. It can do all that base class can, and all that extensions can:

>>> obj = cls()
>>> obj.method1()
'Test'
>>> obj.cool_attribute
1

Extensible

This class provides one more level of abstraction, allowing to hide all metaclass magic behide the scene. So, using it You don’t need to worry about metaclasses and class creation process. Just inherit extensions form base class, and use in Your program instances of base class. Let’s see it in example:

>>> class MyCoolClass(Extensible):
...     my_attr_1 = 25
...     def my_method1(self, arg1):
...         print('Hello, %s' % arg1)

>>> class MyCoolClassExtension1(MyCoolClass):
...     def my_method1(self, arg1):
...         super(MyCoolClassExtension1, self).my_method1(arg1.upper())
...
...     def my_method2(self, arg1):
...         print("Good by, %s" % arg1)

And now using simply instances of base class You have all abilities that provided by extensions:

>>> my_cool_obj = MyCoolClass()
>>> print(my_cool_obj.my_attr_1)
25
>>> my_cool_obj.my_method1('World')
Hello, WORLD
>>> my_cool_obj.my_method2('World')
Good by, World