Read, Write, Analyse & Refine Programs (Edexcel GCSE Computer Science)

Revision Note

Written by: Robert Hampton

Reviewed by: James Woodhouse

Read, Write, Analyse & Refine Programs

With the exception of the final question, which requires students to design and write a program from scratch, questions on paper 2 require students to analyse and refine given code by:
- Correcting errors
- Adding or rearranging lines
- Selecting the correct line
- Improving readability

Correcting errors

Find and correct the errors in this program

Python code - contain errors
# ----------------------------------------------------------------------- # This program calculates the area of a rectangle # ----------------------------------------------------------------------- `lenght = float(input("Enter the lenght of the rectangle: "))` `width = float(input("Enter the width of the rectangle: "))` `area = lenght * width` `print"The area of the rectangle is:", area)` `if area > 100:` `print("This is a large rectangle!")`

Python code - contain errors

# -----------------------------------------------------------------------

# This program calculates the area of a rectangle

# -----------------------------------------------------------------------

lenght = float(input("Enter the lenght of the rectangle: "))

width = float(input("Enter the width of the rectangle: "))

area = lenght * width

print"The area of the rectangle is:", area)

if area > 100:

print("This is a large rectangle!")

This program contain 4 errors:
- Syntax error - typo in variable name lenght (should be length)
- Incorrect use of misspelled variable lenght in area calculation
- Missing bracket in first print statement
- Incorrect indentation for the if statement

Python code - corrected errors
# ----------------------------------------------------------------------- # This program calculates the area of a rectangle # ----------------------------------------------------------------------- `length = float(input("Enter the length of the rectangle: "))` `width = float(input("Enter the width of the rectangle: "))` `area = length * width` `print("The area of the rectangle is:", area)` `if area > 100:` `print("This is a large rectangle!")`

Python code - corrected errors

# -----------------------------------------------------------------------

# This program calculates the area of a rectangle

# -----------------------------------------------------------------------

length = float(input("Enter the length of the rectangle: "))

width = float(input("Enter the width of the rectangle: "))

area = length * width

print("The area of the rectangle is:", area)

if area > 100:

print("This is a large rectangle!")

Adding or rearranging lines

Add lines to the calculate_grade() function to assign letter grades based on the score:
- 90 or above = A
- 80 - 89 = B
- 70 - 79 = C
- Below 70 = F ("Fail")

Python code - incomplete
`def calculate_grade(score):` # ----------------------------------------------------------------------- # This function takes a score as input and returns the corresponding letter grade # ----------------------------------------------------------------------- `def main():` # ----------------------------------------------------------------------- # This function gets user input for a score and calls the calculate_grade function # ----------------------------------------------------------------------- `score = int(input("Enter your score (0-100): "))` `grade = calculate_grade(score)` # Function call `print("Your grade is: ", grade)` # ----------------------------------------------------------------------- # Main program # ----------------------------------------------------------------------- `main()`
Python code - Complete
`def calculate_grade(score):` # ----------------------------------------------------------------------- # This function takes a score as input and returns the corresponding letter grade # ----------------------------------------------------------------------- `if score >= 90:` `return "A"` `elif score >= 80:` `return "B"` `elif score >= 70:` `return "C"` `else:` `return "F"` `def main():` # ----------------------------------------------------------------------- # This function gets user input for a score and calls the calculate_grade function # ----------------------------------------------------------------------- `score = int(input("Enter your score (0-100): "))` `grade = calculate_grade(score)` # Function call `print("Your grade is: ", grade)` # ----------------------------------------------------------------------- # Main program # ----------------------------------------------------------------------- `main()`

Python code - incomplete

def calculate_grade(score):

# -----------------------------------------------------------------------

# This function takes a score as input and returns the corresponding letter grade

# -----------------------------------------------------------------------

def main():

# -----------------------------------------------------------------------

# This function gets user input for a score and calls the calculate_grade function

# -----------------------------------------------------------------------

score = int(input("Enter your score (0-100): "))

grade = calculate_grade(score) # Function call

print("Your grade is: ", grade)

# -----------------------------------------------------------------------

# Main program

# -----------------------------------------------------------------------

main()

Python code - Complete

def calculate_grade(score):

# -----------------------------------------------------------------------

# This function takes a score as input and returns the corresponding letter grade

# -----------------------------------------------------------------------

if score >= 90:

return "A"

elif score >= 80:

return "B"

elif score >= 70:

return "C"

else:

return "F"

def main():

# -----------------------------------------------------------------------

# This function gets user input for a score and calls the calculate_grade function

# -----------------------------------------------------------------------

score = int(input("Enter your score (0-100): "))

grade = calculate_grade(score) # Function call

print("Your grade is: ", grade)

# -----------------------------------------------------------------------

# Main program

# -----------------------------------------------------------------------

main()

Improving readability

Improve the readability of the following program by adding:
- Layout
- White space
- Comments
- Indentation

Python code - poor readability
`total_bill = float(input("Enter the total bill amount: "))` `VAT = 0.20` `tip_prompt = input("Do you want to add a tip? (y/n): ").lower()` `if tip_prompt == 'y':` `tip_percent = float(input("Enter the tip percentage (e.g., 15 for 15%): "))` `tip_amount = total_bill * (tip_percent / 100)` `total_with_tip = total_bill + tip_amount` `else:` `total_with_tip = total_bill` `VAT = total_with_tip * VAT` `final_total = total_with_tip + VAT` `print("Your final bill total is: £", final_total)`
Python code - good readability
`def calculate_bill_total(bill_amount, VAT, tip_percent=0):` # ----------------------------------------------------------------------- """ This function calculates the total bill amount including VAT and optional tip Variables: bill_amount (float): The original bill amount. VAT(float): The tax rate (e.g., 0.20 for 20%). tip_percent (float, optional): The tip percentage (e.g., 15 for 15%). Defaults to 0. Returns: float: The total bill amount including VAT and tip. """ # ----------------------------------------------------------------------- `subtotal_with_tip = bill_amount + (bill_amount * tip_percent / 100)` `VAT = subtotal_with_tip * VAT` `final_total = subtotal_with_tip + VAT` `return final_total` # ----------------------------------------------------------------------- # Get user input # ----------------------------------------------------------------------- `bill_amount = float(input("Enter the total bill amount: "))` `VAT = 0.20 # Assume VAT rate of 20%` # ----------------------------------------------------------------------- # Ask about tip and calculate total # ----------------------------------------------------------------------- `tip_prompt = input("Do you want to add a tip? (y/n): ").lower()` `if tip_prompt == 'y':` `tip_percent = float(input("Enter the tip percentage (e.g., 15 for 15%): "))` `else:` `tip_percent = 0` `final_total = calculate_bill_total(bill_amount, VAT, tip_percent)` # ----------------------------------------------------------------------- # Print the final bill total # ----------------------------------------------------------------------- `print("Your final bill total is: £", final_total)`

Python code - poor readability

total_bill = float(input("Enter the total bill amount: "))

VAT = 0.20

tip_prompt = input("Do you want to add a tip? (y/n): ").lower()

if tip_prompt == 'y':

tip_percent = float(input("Enter the tip percentage (e.g., 15 for 15%): "))

tip_amount = total_bill * (tip_percent / 100)

total_with_tip = total_bill + tip_amount

else:

total_with_tip = total_bill

VAT = total_with_tip * VAT

final_total = total_with_tip + VAT

print("Your final bill total is: £", final_total)

Python code - good readability

def calculate_bill_total(bill_amount, VAT, tip_percent=0):

# -----------------------------------------------------------------------

"""

This function calculates the total bill amount including VAT and optional tip

Variables:

bill_amount (float): The original bill amount.

VAT(float): The tax rate (e.g., 0.20 for 20%).

tip_percent (float, optional): The tip percentage (e.g., 15 for 15%). Defaults to 0.

Returns:

float: The total bill amount including VAT and tip.

"""

# -----------------------------------------------------------------------

subtotal_with_tip = bill_amount + (bill_amount * tip_percent / 100)

VAT = subtotal_with_tip * VAT

final_total = subtotal_with_tip + VAT

return final_total

# -----------------------------------------------------------------------

# Get user input

# -----------------------------------------------------------------------

bill_amount = float(input("Enter the total bill amount: "))

VAT = 0.20 # Assume VAT rate of 20%

# -----------------------------------------------------------------------

# Ask about tip and calculate total

# -----------------------------------------------------------------------

tip_prompt = input("Do you want to add a tip? (y/n): ").lower()

if tip_prompt == 'y':

tip_percent = float(input("Enter the tip percentage (e.g., 15 for 15%): "))

else:

tip_percent = 0

final_total = calculate_bill_total(bill_amount, VAT, tip_percent)

# -----------------------------------------------------------------------

# Print the final bill total

# -----------------------------------------------------------------------

print("Your final bill total is: £", final_total)

Last updated: 1 April 2024

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Read, Write, Analyse & Refine Programs (Edexcel GCSE Computer Science)

Revision Note

Read, Write, Analyse & Refine Programs

Correcting errors

Adding or rearranging lines

Improving readability

You've read 0 of your 5 free revision notes this week

Sign up now. It’s free!

Join the 100,000+ Students that ❤️ Save My Exams

Author: Robert Hampton

Author: James Woodhouse