Why Use Operator Overloading?

As a class designer, you can choose to use operator overloading or not. Your choice simply depends on how much you want your object to look and feel like built-in types. As mentioned earlier, if you omit an operator overloading method and do not inherit it from a superclass, the corresponding operation will not be supported for your instances; if it’s attempted, an exception will be thrown (or a standard default will be used).

Frankly, many operator overloading methods tend to be used only when implementing objects that are mathematical in nature; a vector or matrix class may overload the addition operator, for example, but an employee class likely would not. For simpler classes, you might not use overloading at all, and would rely instead on explicit method calls to implement your objects’ behavior.

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On the other hand, you might decide to use operator overloading if you need to pass a user-defined object to a function that was coded to expect the operators available on a built-in type like a list or a dictionary. Implementing the same operator set in your class will ensure that your objects support the same expected object interface and so are compatible with the function. Although we won’t cover every operator overloading method in this book, we’ll see some additional operator overloading techniques in action in Chapter 29.

One overloading method we will explore here is the __init__ constructor method, which seems to show up in almost every realistic class. Because it allows classes to fill out the attributes in their newly created instances immediately, the constructor is useful for almost every kind of class you might code. In fact, even though instance attributes are not declared in Python, you can usually find out which attributes an instance will have by inspecting its class’s __init__ method.

 

[60] Not to be confused with the __init__.py files in module packages! See Chapter 23 for more details.