Python Programming

Department of Computing | Imperial College London

book

Lesson 8

Making Objects the Main Star!

Chapter 3: Classes and attributes

Class definition and instantiation

face Josiah Wang

Now, let’s delve deeper into designing classes, step by step! Please follow along and try it yourself!

Let’s stick with defining a Person class. I have given you the minimum form of a class definition. Quite straightforward!

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class Person:
    pass

Our favourite PEP 8 states that “class names should normally use the CapWords convention”. So name your objects in CapWords (also known as PascalCase), like YorkshireTerrier or ComputerMonitor.

I am enforcing this strictly for this course. So please use PascalCase for your ClassName. This helps you distinguish between variables and function names (which should both be in lowercase) much better. It is also the convention in most programming languages anyway!

You can now create a new instance of your brand new Person class (although it is not quite useful at the moment!)

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class Person:
    pass

manager = Person()
print(manager)
print(isinstance(manager, Person))

The code should output something like <__main__.Person object at 0x7fe70c878c10> for Line 5. So manager points to the object of class Person at memory location 0x7fe70c878c10. We will talk about __main__ in the next chapter - it will make more sense then!

The built-in isinstance() function (Line 6) will return True if your object is an instance of a given class.

In essence, you have created a new instance of class Person!

Class instantiation