Decorators can be a bit mind-bending when first encountered and they can also be a bit tricky to debug. But they are a neat way to add functionality to functions and classes. Decorators are also known as a “higher-order function.” What this means is that they can take one or more functions as arguments and return a function as its result. In other words, decorators will take the function they are decorating and extend its behavior while not actually modifying what the function itself does.
There have been two decorators in Python since version 2.2, namely classmethod() and staticmethod(). Then PEP 318 was put together and the decorator syntax was added to make decorating functions and methods possible in Python 2.4. Class decorators were proposed in PEP 3129 to be included in Python 2.6. They appear to work in Python 2.7, but the PEP indicates that they weren’t accepted until Python 3, so I’m not sure what happened there.