Good little introduction in terms of general use, but I think a solid example is in order, as it's a very useful technique.

A while back, I created a Struct class, which allows the creation of C-like structs, but you had to create a subclass of Struct, specify the endianness as a class attribute, and create a __format__ method that built the struct members. A little while ago, I had the thought to wrap it into a decorator, defStruct/defStructLE/defStructBE, that automagickly calls 'type' to build the appropriate Struct class for you, given a method.

So what once was:

    class Foo(Struct):
      __endian__ = Struct.LE
      def __format__(self):
        self.foo = Struct.uint32
        self.bar = Struct.string(self.foo)

Became:

    @defStructLE
    def Foo(self):
      self.foo = Struct.uint32
      self.bar = Struct.string(self.foo)

Much, much cleaner, all thanks to the magic of 'type'.