Missing miscellaneous magic methods

[rhettinger]

The dir magic method is used by the built-in dir() function. All classes inherit this method, but it can be extended or overridden to control what is shown in a dir() listing. The main use case is for classes that add methods dynamically (ORMs and whatnot).

Also, there is a sizeof magic method called by sys.getsizeof().

And there is subclasshook magic method used to create abstract base classes.