- 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?

#code here

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

# Code here
def subtract(parameter1, parameter2):
    solution = parameter1 - parameter2
    return solution
subtract(2,4)
    

-2

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__(name, model_year, price):
        car.name = name
        car.model_year = model_year
        car.price = price

Homework:

Assignment 1: How do you use functions?

Create a turtle python function that...

  1. Takes a single parameter as the number of sides
  2. Outputs a shape corresponding to the number of sides
  3. Call the function with the argument being a variable with the user input

Hint: 

import turtle

pen = turtle.Turtle(); # pen is the instance of Turtle which has methods that do certain actions

# Necessary methods:
# .forward(50) - moves the pen forward 50 units
# .right(angle) - turns the pen angle degrees right   
# OR
# .left(angle) - turns the pen angle degrees left


angle = 0
sides = int(input("How many sides? "))
if sides == 1 or sides == 2:
    print("Please enter a shape")
else:
    angle = 360/sides
    

for i in range(sides):
    pen.forward(30)
    pen.right(angle)
    i += 1

turtle.exitonclick()  # Close the window by clicking

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 person:
    def __init__(self, email, name, grade, ): # constructor
        self.email = email
        self.name = name
        self.grade = grade
    
    def getEmail(self): # method to create get email
        return self.email
    
    def getName(self): # method to create get name
        return self.name
    
    def getGrade(self): # method to create get grade
        return self.grade
    
    def setEmail(self, email): # method to create set email
        self.email = email
    
    def setName(self, name): # method to create set name
        self.name = name
        
    def setGrade(self, grade): # method to create set grade
        self.grade = grade
        
    def __str__(self): # method that returns a string when the object is printed
        return ("My name is " + self.name + " and I am in " + str(self.grade) + "th grade. My email is " + self.email)

me = person('x@gmail.com', 'Samhita Lagisetti', 10)
print(me)

My name is Samhita Lagisetti and I am in 10th grade. My email is x@gmail.com