9.3.2 Class Objects

Class objects support two kinds of operations: attribute references and instantiation.

Attribute references use the standard syntax used for all attribute references in Python: obj.name. Valid attribute names are all the names that were in the class's name space when the class object was created. So, if the class definition looked like this:

class MyClass:
    "A simple example class"
    i = 12345
    def f(x):
        return 'hello world'

then MyClass.i and MyClass.f are valid attribute references, returning an integer and a function object, respectively. Class attributes can also be assigned to, so you can change the value of MyClass.i by assignment. __doc__ is also a valid attribute that's read-only, returning the docstring belonging to the class: "A simple example class").

Class instantiation uses function notation. Just pretend that the class object is a parameterless function that returns a new instance of the class. For example, (assuming the above class):

x = MyClass()

creates a new instance of the class and assigns this object to the local variable x.