Object Oriented Programming

What is OOP?

OOP stands for Object Oriented Programming. It is a computer programming model that focuses on classes and objects.

General structure of a program that uses OOP

• Classes- user-defined data types that act as the blueprint for the program
• Objects - instances of a class created with specific data
• Methods- user-defined functions, within a class, that define the behaviour of an object
• Attributes- information, defined within a class, that define the state of an object

The 4 pillars of OOP

Encapsulation

Definition

This concept refers to the protection of information contained in an object. It restricts the access to sensitive information and only select information is exposed. Information can be:

• Public- accessible from within the class or outside the class
• Protected- accessible from within the class and it's sub-classes (denoted by an _ at the start)
• Private- accessible only from within the class (denoted by __ at the start)

Example

In this example you can see where I have used public and protected information when initialising my attributes.

self.oest_dominant = False
self.__job = job   # private info that is only stored in this class

Abstraction

Definition

This details the fact that objects only reveal internal mechanisms that are relevant, thus hiding any unnecessary implementation of code.

Example

This example demonstrates the object being able to call a method, but the user doesn't need to see what information was required to build that method.

fahim = Male()   # object of the Male class
fahim.drink()   # this is part of the Human class but can still be used as its inherited

Inheritance

Definition

Inheritance refers to the re-usability of code as code can be 'inherited' from other classes.

Example

You can see how the Male class is a child class of the Human class due to inheritance.

# Create Male child class of Human parent class
from human import Human
class Male(Human):

Polymorphism

Definition

Objects are designed to share behaviours and can take on more than one form.

Example

This example shows how the same method has taken on different forms depending on the class it is in.

# From Female class
def get_married(self):
    return print("I want to get married one day and be a bride")

# From Male class
def get_married(self):
    return print("I want to get married one day and be a groom")

Jargon

• pass- this is used as a placeholder, so that code can be edited in its place later.
• super()- this function is used to allow a child class to inherit methods and attributes from a parent class.
• init()- this function is used to initialise attributes that belong to a class.

Appendix

Appendix A: Human Class

class Human:

    def __init__(self):  # initialise the attributes that will be part of this class and inherited by each child class
        self.eyes = True
        self.nose = True
        self.mouth = True

    def sleep(self, name):   # method to show you can have variables that are specific to methods that don't belong to the whole class
        return print(f"{name.capitalize()} likes to sleep for 8 hours")

    def eat(self, no_meals):   # once an object of the class is made, the method requires another input
        return print(f"I like to eat {no_meals} meals a day")

    def drink(self):
        fav_drink = input("What is your favourite drink? ")
        return print(f"I like to drink {fav_drink}")

Appendix B: Male Class

# Create Male child class of Human parent class
from human import Human

class Male(Human):

    def __init__(self, job):
        super().__init__()   # super is used to inherit everything from parent class and initialises it in the child class
        self.pregnancy = False
        self.test_dominant = True
        self.oest_dominant = False
        self.__job = job   # private info that is only stored in this class

    def go_to_work(self):
        return print("I like to work to earn money")

    def paternity_leave(self):
        return print("If I have a child, I will get paternity leave")

    def get_married(self):
        return print("I want to get married one day and be a groom")

Appendix C: Female Class

# Create child class called Female of the Male class for re-usability of code
from male import Male

class Female(Male):   # inheriting from Male class for efficiency

    def __init__(self):
        super().__init__()
        self.pregnancy = True   # change the attributes to be specific to the female class
        self.test_dominant = False
        self.oest_dominant = True

    def paternity_leave(self):   # cannot remove a method from parent class after inheritance, so edited to be class specific
        pass

    def maternity_leave(self):
        return print("If I have a child, I will get maternity leave")

    def get_married(self):
        return print("I want to get married one day and be a bride")   # editing a method from Male class to be Female class specific

    def give_birth(self):   # define a new function that is only in this child class
        return print("If I get")

Appendix D: Boy Class

# Create class that inherits from Human class
from human import Human

class Boy(Human):

    def __init__(self):
        super().__init__()
        self.school = True
        self.deep_voice = True
        self.high_voice = False

    def play(self):
        return print("I like to play all day")

    def go_to_school(self):
        return print("I go to an all boys school")

    def homework(self):
        return print("I hate doing homework")

Appendix E: Girl Class

# Create child class called girl that inherits from the Boy class
from boy import Boy

class Girl(Boy):

    def __init__(self):
        super().__init__()
        self.deep_voice = False
        self.high_voice = True

    def go_to_school(self):
        return print("I go to an all girls school")