Objects and Classes (Basic OOP)

• every object has a type, an internal data representation (a blueprint), a set of procedures for interacting with the object (method)
• An object is an instance of a particular type
• e.g Type 1: Object 1, Object 2,...

Objects

Types

• using type() to find the type of an object

print(type(1))

Output

<class 'int'>

print(type('kevin'))

Output

<class 'str'>

Methods

• for example: .sort(), .append(), .add()

Classes

Defining classes

• Class includes both Data attributes & Methods
• You can create classes, for examples:

Class Car

-> Data attributes: brand, color

class Car:  # define your class

    def __init__(self, brand, color):  # self is self parameter
        # brand and color are parameters
        self.brand = brand
        self.color = color
# those are data attributes used to initialize each instance of the class

my_car = Car('VinFast', 'red')
print(my_car.brand, my_car.color)

Output

VinFast red

Create an instance of a Class: Car

class Car(object):  # (object) is optional, in Python 2 we don't need (object)
    def __init__(self, brand, color):
        self.brand = brand
        self.color = color

    def drive(self):
        print(f"The {self.color} {self.brand} is driving")

VinFast = Car('VinFast', 'red')

VinFast.drive()

Output

The red VinFast is driving

# NO __init__
class ToanTinTCTA:
    pass
    # this class is completely empty, no automatically assign a value or anything

# So now, if we want to create 2 individuals:
person1 = ToanTinTCTA()
person2 = ToanTinTCTA()
# U have to manually assign values to them, cuz its not automatic
person1.name = "Hong Phuc"
person1.username = "kevinph4n"

person2.name = "Hung Dan"
person2.username = "hungdan"

print(person1.name)

Output

Hong Phuc

# WITH __init__
class ToanTinTCTA:
    def __init__(self, name, username):
        self.name = name
        self.username = username

person1 = ToanTinTCTA("Hong Phuc", "kevinph4n")
person2 = ToanTinTCTA("Hung Dan", "hungdan")

print(person1.name)

Output

Hong Phuc

More examples (OOP Intermediate)

# Class
class WorldCup:
    pass

print(WorldCup)

Output

<class '__main__.WorldCup'>

# Object
class WorldCup:
    pass

Messi = WorldCup()
print(type(Messi).__name__)

Output

WorldCup

# Variables bound to an object
class WorldCup_0:
    def __init__(self, full_name, won_the_wc, has_a_wife):
        self.full_name = full_name
        self.won_the_wc = won_the_wc
        self.has_a_wife = has_a_wife

messi = WorldCup_0("Lionel Messi", "Yes", "1 Wife")
print(messi.full_name)
print(messi.won_the_wc)
print(messi.has_a_wife)

Output

Lionel Messi
Yes
1 Wife

class WorldCup_1:
    def trash_talk(self):  # Method
        print("I have money!")

messi = WorldCup_1()
messi.trash_talk()

Output

I have money!

# Inheritance: Child class inherits from parent class

class Athlete:
    pass

class Fighter(Athlete):  # Inheritance
    pass

print(issubclass(Fighter, Athlete))

Output

True

# Example using inheritance

class WorldCup_2:

    def height(self, height):
        # Maps height to height class
        return "Short"

# Footballer class inherits from WorldCup_2
class Footballer(WorldCup_2):

    def __init__(self, name):
        self.name = name

    def print_name(self):
        print(self.name)

footballer = Footballer("Messi")
print(footballer.height(160))
footballer.print_name()

Output

Short
Messi

class student:
    def __init__(self, name, age, GPA):
        self.GPA = GPA
        self.name = name
        self.age = age

HungDan = student("Hung Dan", 21, 4.0)
HongPhuc = student("Hong Phuc", 18, 4.0)

print("HongPhuc's age: ", HongPhuc.age)
print("HungDan's GPA: ", HungDan.GPA)

Output

HongPhuc's age:  18
HungDan's GPA:  4.0