Functions and Classes in Python

Table of contents

• Functions
• Classes
• How to create a class
• Attributes in class
• Methods in class
• The init method

Functions

How to create a function

def Car(n):
    print('My car is Toyota!'+n)

Car('health ')
My car is Toyota!
def Car(carname):
    print('My car is ' + carname + '!')

Car('Ford')
My car is Ford!

Write a Car function with price as a parameter that performs the following conditional actions:

• if price is above 20,000, print “It is expensive!”.
• if price is less than 20,000 and above 10,000 print “It is reasonable!”.
• Otherwise, print “It is cheap!”.

def Car(price):
    if price >= 20000:
        print("It is expensive!")
    elif price >= 10000:
        print("It is reasonable!") 
    else:
        print("It is cheap!")  

price = 9000        
Car(price)

Write a function to compute factorial of a number. The factorial of a number is the product of all the integers from 1 to that number.

def factorial(x):
    f = 1
    
    for i in range(1,x+1):
        f = f*i
    return f

factorial(4)

Classes

How to create a class

class Car:
    pass

car = Car() # instantiate the class Car and assign it to the variable car
print(car)

Attributes in class

class Car:
    name = "Toyota" # set an attribute `name` of the class

car = Car() 

print(car.name) # access the class attribute name inside the class Car

Methods in class

class Car:
    name = "Toyota"
    
    def change_name(self, new_name): # note that the first argument is self
        self.name = new_name # access the class attribute with the self keyword

        
car = Car() 

print(car.name)

car.change_name("Ford")
print(car.name)
Toyota
Ford
class Car:
    self.name = "Toyota"

        
car = Car() 

print(car.name)

The init method

class Car:
    
    def __init__(self, name): # In order to provide values for the attributes at runtime
        self.name = name
        
    def change_name(self, new_name): 
        self.name = new_name

car_t = Car('Toyota') 
print(car_t.name)

car_f = Car('Ford') 
print(car_f.name)

car_f.change_name("Benz")
print(car_f.name)

Write a Car class with an instance variable, price, and a constructor that takes a float, base_price, as a parameter. The constructor must assign base_price to price after confirming the argument passed as base_price is not negative; if a negative argument is passed as base_price, the constructor should set price to 0 and print “price is not valid, setting price to 0”. In addition, write Is_it_expensive() instance method that performs the following conditional actions:

• if price is above 20,000, print “It is expensive!”.
• if price is less than 20,000 and above 10,000 print “It is reasonable!”.
• Otherwise, print “It is cheap!”.

class Car:
    def __init__(self, base_price):
        if base_price > 0:
            self.price = base_price
        else:
            print("price is not valid, setting price to 0")
            self.price = 0   
    
    def Is_it_expensive(self):
        
        if self.price >= 20000:
            print("It is expensive!")
        elif self.price >= 10000:
            print("It is reasonable!") 
        else:
            print("It is cheap!")  

price = 11000        
car = Car(price) 
car.Is_it_expensive()