15.7. Object-Oriented Buzzwords¶
Explanations of OOP often begin with a lot of jargon, such as inheritance, encapsulation, and polymorphism. The importance of knowing these terms is overrated, but you should have at least a basic understanding of them. I already covered inheritance, so I’ll describe the other concepts here. ## Encapsulation The word encapsulation has two common but related definitions. The first definition is that encapsulation is the bundling of related data and code into a single unit. To encapsulate means to box up. This is essentially what Object-Oriented Programming and Inheritance 307classes do: they combine related attributes and methods. For example, our WizCoin class encapsulates three integers for knuts, sickles, and galleons into a single WizCoin object.
The second definition is that encapsulation is an information hiding technique that lets objects hide complex implementation details about how the object works. You saw this in “Private Attributes and Private Methods” on page 282, where BankAccount objects present deposit() and withdraw() methods to hide the details of how their _balance attributes are handled. Functions serve a similar black box purpose: how the math.sqrt() function calculates the square root of a number is hidden. All you need to know is that the function returns the square root of the number you passed it. ## Polymorphism Polymorphism allows objects of one type to be treated as objects of another type. For example, the len() function returns the length of the argument passed to it. You can pass a string to len() to see how many characters it has, but you can also pass a list or dictionary to len() to see how many items or key-value pairs it has, respectively. This form of polymorphism is called generic functions or parametric polymorphism, because it can handle objects of many different types.
Polymorphism also refers to ad hoc polymorphism or operator overload- ing, where operators (such as + or * ) can have different behavior based on the type of objects they’re operating on. For example, the + operator does mathematical addition when operating on two integer or float values, but it does string concatenation when operating on two strings. Operator over- loading is covered in Chapter 17.