The Basics

Really “operator overloading” simply means intercepting built-in operations in class methods—Python automatically invokes your methods when instances of the class appear in built-in operations, and your method’s return value becomes the result of the corresponding operation. Here’s a review of the key ideas behind overloading:

 

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  • Operator overloading lets classes intercept normal Python operations.
  • Classes can overload all Python expression operators.
  • Classes can also overload built-in operations such as printing, function calls, attribute access, etc.
  • Overloading makes class instances act more like built-in types.
  • Overloading is implemented by providing specially named class methods.

In other words, when certain specially named methods are provided in a class, Python automatically calls them when instances of the class appear in their associated expressions. As we’ve learned, operator overloading methods are never required and generally don’t have defaults; if you don’t code or inherit one, it just means that your class does not support the corresponding operation. When used, though, these methods allow classes to emulate the interfaces of built-in objects, and so appear more consistent.