Expert Python Programming - Third Edition

Creational patterns

Creational patterns deal with the object instantiation mechanism. Such a pattern might define a way for object instances to be created or even how classes are constructed.

These are very important patterns in compiled languages such as C or C++, since it is harder to generate types on demand at runtime.

But creating new types at runtime is pretty straightforward in Python. The built-in type function lets you define a new type object by code:

>>> MyType = type('MyType', (object,), {'a': 1})
>>> ob = MyType()
>>> type(ob)
<class '__main__.MyType'>
>>> ob.a
1
>>> isinstance(ob, object)
True

Classes and types are built-in factories. We have already dealt with the creation of new class objects, and you can interact with class ...