- CB 3.12,3.13 Developing Procedures

What is a procedure?

A procedure is a named group of code that has paramaters and return values. Procedures are known as methods or functions depending on the language.

A procedure executes the statements within it on the parameters to provide a return value.

What are parameters?

Paramaters are input values of a procedure that are specified by arguments.Arguments specify the values of the parameters when a procedure is called.

By creating theses algorithms the readibility of code increases and the complexity decreases. This is becasue a function’s name can tell the reader what action it will perform, and by calling it, the code becomes more clean and easy to understand.

What is a return value?

A return value is the value that is returned when a function or a method is called.

That return value can be assigned or printed

Procedures are used to create algorthims that can perform certain actions or return values. When a procedure returns a value, theis information must be stored in a variable for later use. However some procedures like the MOVE_FORWARD() perform an action, and don’t return a value. The image above provides an example of where procedures that don’t output a value would be used.

A 60$ item recieves a 20% discount and taxed at 8%.
PROCEDURE applyDiscount(cost, percentDiscounted)
{
    temp ← 100 - percentDiscounted
    temp← temp/ 100
    cost ← cost *temp
    RETURN(cost)
}

price ← applyDiscount(60, 20)
This is how we get the final price with the discount by calling the procedure and assigning it to the price variable.


PROCEDURE applyTax(cost, percentTaxed)
{
    temp ← 100 + percentTaxed
    temp← temp/ 100
    cost ← cost *temp
    RETURN(cost)
}
price ← applyTax(price, 8)
This applys the 8% tax to the price determined after the discount.

Popcorn Hack 1

Given the applyTax procedure above: How would you call the procedure to get it to find the price using cost = 50, and percentTaxed = 10, and what value will it return?

def applyTax(cost, percentTaxed):
    temp = 100 + percentTaxed
    temp = temp/100
    cost = cost * temp
    return cost

applyTax(50, 10)

55.00000000000001

What Are Functions?

  • Collections of code
  • Divides large program into smaller chunks
  • Better readability
  • Less repetitive code
  • More efficient code
  • Good organization

What Are The Components of a Function?

  • The function declaration
  • The parameters (input). This is also referred to as an argument when a value is being passed to the actual function.
  • The functionality
  • The return value (output)
  • Calling the function
# Defining Functions
#
# def function_name(parameter1, parameter2, etc..):
#     code here...
#
#     return return_value;

# return the value of parameter1 plus parameter2;
def add(parameter1, parameter2): # creates a function that takes in two parameters
    solution = parameter1 + parameter2; # sets solution to the sum of parameter1 and parameter2
    return solution; # return solution
    
print(add(5, 5)); # prints the return value of add(5,5)

Popcorn Hack 2:

1. Make a function that returns the difference of two numbers

def subtract(parameter1, parameter2):
    solution = parameter1 - parameter2;
    return solution;

subtract(10, 5)

5

What is a Class?

  • A class is an outline for a set of nested functions and variables.
  • There are instance variables
  • Functions
    • Constructor method (Required)
    • To String method
    • Getter method
    • Setter method

How Does a Class Work?

# Defining Classes
class person:
    def __init__(self, name, age, ): # constructor
        self.name = name;
        self.age = age;
    
    def getName(self): # method to create get name
        return self.name;
    
    def getAge(self): # method to create get age
        return self.age;
    
    def setName(self, name): # method to create set name
        self.name = name;
        
    def setAge(self, age): # method to create set age
        self.age = age;
        
    def yearOlder(self): # method to increment age by 1
        self.age += 1;
        
    def __str__(self): # method that returns a string when the object is printed
        return (f"My name is {self.name} and I am {self.age} years old.")

Person1 = person("John Doe", 15);
print(Person1)


print(Person1);

Popcorn Hack 3:

1. Create a Car class which has the attributes model, vehicle name, and price

2. Create instances of the following cars

  • Name: Honda Civic , Model Year: 2018 , Price: $13,000
  • Name: Toyota Prius, Model Year: 2023 , Price: $28,000
  • Name: Chevrolet Impala, Model Year: 2020 , Price: $22,000 
class Car:
    def __init__(self, model, name, price):
        self.model = model
        self.name = name
        self.price = price
    
    def getModel(self):
        return self.model
    
    def getName(self):
        return self.name
    
    def getPrice(self):
        return self.price
    
    def setModel(self, model):
        self.model = model
    
    def setName(self, name):
        self.name = name
    
    def setPrice(self, price):
        self.price = price
    
    def __str__(self):
        return (f"Model: {self.model}\nName: {self.name}\nPrice: {self.price}")
    

car1 = Car(2018, "Honda Civic", 13000)
car2 = Car(2023, "Toyota Prius", 28000)
car3 = Car(2020, "Chevrolet Impala", 22000)

print(car1)
print(car2)
print(car3)

Model: 2018
Name: Honda Civic
Price: 13000
Model: 2023
Name: Toyota Prius
Price: 28000
Model: 2020
Name: Chevrolet Impala
Price: 22000

Homework:

Assignment 1: How do you use functions?

Create a function that takes in an array as the parameter and returns the array of distinct values. DON'T USE SETS

arr1 = [2,1,3,2,0,2,0,0,4,2,0,0,0,2,0,0,1,2,3,0,7,4,5,2,1,2,3,4,6]

def distinct_values(arr):
    distinct_arr = []
    for i in arr:
        if i not in distinct_arr:
            distinct_arr.append(i)
    return distinct_arr

distinct_values(arr1)

[2, 1, 3, 0, 4, 7, 5, 6]

Assignment 2:

Create a student class that...

  1. Has a constructor that takes three parameters as attributes
    • email
    • name
    • grade
  3. Three getter methods to access the name, email, and grade
  4. Three setter methods to modify the name, email, and grade
  5. A to string method that returns the three instance variables in this format - "My name is {name}. My email is {email}. My grade is {grade}
  6. Create an instance of the class that corresponds with you
class Student:
    def __init__(self, email, name, grade):
        self.email = email
        self.name = name
        self.grade = grade
    
    def get_email(self):
        return self.email
    
    def get_name(self):
        return self.name
    
    def get_grade(self):
        return self.grade
    
    def set_email(self, email):
        self.email = email
    
    def set_name(self, name):
        self.name = name
    
    def set_grade(self, grade):
        self.grade = grade
    
    def __str__(self):
        return f"My name is {self.name}. My email is {self.email}. My grade is {self.grade}"

my_student = Student("kumeshsd@gmail.com", "Eshaan", 11)
print(my_student)


My name is Eshaan. My email is kumeshsd@gmail.com. My grade is 11