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Objects And Classes

Central concepts are the ideas of classes and objects, which form the basis of Object-Oriented (OO) programming. Not too much in-depth knowledge of these topics is required but it is useful to understand the basics.

Object Orientation

Any program is essentially a collection of actions that are applied to some data.

In an OO design, the data and actions are broken down and combined to form objects that model parts of the “system”.

The objects are then combined together to form the program as a whole.

Classes

A class is a blueprint that is used to construct an object, i.e. tells it what data it knows about and what actions can be applied to it.

In Python this is done using the class keyword, for example, a Person class with a single piece of data (attribute) that stores their name would look like:

class Person(object):
    name = "Bob"

The class is used by constructing an object that is defined by the given class and then accessing the attributes:

person_object = Person()
print(person_object.name)

The attributes can be changed but the changes apply to that object and not the class, i.e. the blueprint is not affected:

person_object1 = Person()
person_object1.name = 'Alice'

person_object2 = Person()
print("Person 1 name: " + person_object1.name)  # => prints Alice
print("Person 2 name: " + person_object2.name)  # => prints Bob

Contents

• Methods

• Inheritance

• Exercise 1