Using special methods for attribute access

We'll look at the three canonical special methods for attribute access: __getattr__(), __setattr__(), and __delattr__(). Additionally, we'll acknowledge the __dir__() method to reveal attribute names. We'll defer __getattribute__() to the next section.

The default behavior shown in the first section is as follows:

• The __setattr__() method will create and set attributes.

• The __getattr__() method will do two things. Firstly, if an attribute already has a value, __getattr__() is not used; the attribute value is simply returned. Secondly, if the attribute does not have a value, then __getattr__() is given a chance to return a meaningful value. If there is no attribute, it must raise an AttributeError exception.

• The __delattr__() method deletes an attribute.

• The __dir__() method returns a list of attribute names.

The __getattr__() method function is only one step in a larger process; it is only used if the attribute is otherwise unknown. If the attribute is...