What are the variables prefixed with two underscores (_ _)(_ _) in classes called?

Variables that are prefixed with two underscores (__) in classes are called "dunder" variables or "magic" methods in Python. These are special methods that Python uses for specific operations, often related to operator overloading. They are also used to create functionality that can't be represented as a normal method.

For example, __init__ is a magic method that is used for the initialization of an object. It's called when an object is created from a class. Another example is __str__, which is used to represent a class object as a string.

These methods are automatically invoked by Python when a certain type of operation is performed on the class or its instances. They are not meant to be invoked directly.