Student Marks Average Calculator

1) Project Overview

This project helps a student enter marks for their subjects and then calculates the average. The program:

Asks how many subjects there are.
Asks for each mark (for example, out of 100).
Calculates the total and the average.
Shows helpful information like highest and lowest mark.

It's simple, interactive, and perfect for practicing basic Python skills.

2) Learning Objectives

By completing this project, students will:

Use input() and print() to interact with the user.
Store data in variables and lists.
Use loops (for and while) to repeat actions.
Use if statements to check conditions (e.g., valid numbers).
Convert strings to numbers (int and float).
Do basic math (sum, average).
Format output neatly and write clear comments.

3) Step-by-Step Explanation

Plan the inputs and outputs
- Input: number of subjects (a positive whole number).
- Input: each subject's mark (a number from 0 to 100).
- Output: the list of marks, total, average (rounded), highest and lowest mark.
Start the program with a friendly message
- Print a welcome line so the user knows what the program does.
Ask for the number of subjects
- Use input().
- Convert to int.
- Keep asking until the number is a positive integer.
Collect the marks in a list
- Use a for loop to ask for each mark.
- Convert to float (marks can have decimals like 92.5).
- Check that each mark is between 0 and 100.
- If the user types something invalid, ask again.
Calculate total and average
- Use sum(marks) for total.
- Average = total / number of subjects.
Show the results neatly
- Print each mark with its subject number.
- Print the total and average (rounded to 2 decimal places).
- Print the highest and lowest mark.
End with a friendly message
- Encourage the user or suggest what to try next.

4) Complete and Well-Commented Python Code

You can copy and paste this into a file named marks_average_calculator.py and run it.

Try it Yourself »

# Student Marks Average Calculator

print("Welcome to the Student Marks Average Calculator!")
print("This program will calculate the average of your subject marks.\n")

# Step 1: Ask for the number of subjects (must be a positive whole number)
while True:
    subjects_text = input("How many subjects do you have? ")
    try:
        num_subjects = int(subjects_text)
        if num_subjects <= 0:
            print("Please enter a number greater than 0.")
        else:
            break  # valid number of subjects
    except ValueError:
        print("That's not a whole number. Please try again.")

# Step 2: Collect marks for each subject in a list
marks = []  # this list will store all the marks entered

for i in range(1, num_subjects + 1):
    while True:
        mark_text = input(f"Enter mark for Subject {i} (0 to 100): ")
        try:
            mark = float(mark_text)  # marks can be decimal numbers
            if 0 <= mark <= 100:
                marks.append(mark)
                break  # valid mark, go to next subject
            else:
                print("Mark must be between 0 and 100. Please try again.")
        except ValueError:
            print("That doesn't look like a number. Please try again.")

# Step 3: Calculate total and average
total = sum(marks)
average = total / num_subjects

# Step 4: Show results neatly
print("\n----- Results -----")
print(f"Number of subjects: {num_subjects}")

print("Marks you entered:")
for i, m in enumerate(marks, start=1):
    # :.2f means show the number with 2 decimal places
    print(f"  Subject {i}: {m:.2f}")

print(f"\nTotal of marks: {total:.2f}")
print(f"Average mark: {average:.2f}")

# Extra helpful info:
highest_mark = max(marks)
lowest_mark = min(marks)
print(f"Highest mark: {highest_mark:.2f}")
print(f"Lowest mark: {lowest_mark:.2f}")

# A friendly closing message
if average >= 90:
    print("Excellent work! Keep it up!")
elif average >= 70:
    print("Good job! You're doing well.")
else:
    print("Keep practicing—you can improve with a bit more study.")

print("\nThank you for using the Student Marks Average Calculator!")

5) Output Examples

Example 1: A smooth run

Welcome to the Student Marks Average Calculator!
This program will calculate the average of your subject marks.

How many subjects do you have? 4
Enter mark for Subject 1 (0 to 100): 85
Enter mark for Subject 2 (0 to 100): 92.5
Enter mark for Subject 3 (0 to 100): 78
Enter mark for Subject 4 (0 to 100): 66

----- Results -----
Number of subjects: 4
Marks you entered:
  Subject 1: 85.00
  Subject 2: 92.50
  Subject 3: 78.00
  Subject 4: 66.00

Total of marks: 321.50
Average mark: 80.38
Highest mark: 92.50
Lowest mark: 66.00
Good job! You're doing well.

Thank you for using the Student Marks Average Calculator!

Example 2: Handling invalid input

How many subjects do you have? -3
Please enter a number greater than 0.
How many subjects do you have? two
That's not a whole number. Please try again.
How many subjects do you have? 2
Enter mark for Subject 1 (0 to 100): 120
Mark must be between 0 and 100. Please try again.
Enter mark for Subject 1 (0 to 100): ninety
That doesn't look like a number. Please try again.
Enter mark for Subject 1 (0 to 100): 90
Enter mark for Subject 2 (0 to 100): 80

----- Results -----
Number of subjects: 2
Marks you entered:
  Subject 1: 90.00
  Subject 2: 80.00

Total of marks: 170.00
Average mark: 85.00
Highest mark: 90.00
Lowest mark: 80.00
Good job! You're doing well.

6) Small Exercise (Challenge)

Add a grade message based on the average

If average >= 90: print "Grade A"
If 80–89.99: print "Grade B"
If 70–79.99: print "Grade C"
If 60–69.99: print "Grade D"
If below 60: print "Grade E"

Tip: Use if/elif/else after calculating the average.

Extra idea: Also ask for subject names and print a tiny report like "Math: 85.00".

7) Summary

Great job! You built a working program that takes user input, validates it, stores it in a list, uses loops and conditions, and calculates an average. These are core programming skills you'll use in many projects. Keep practicing, try the challenge, and have fun improving your calculator!

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