Project: marks and grade calculator: Python Programming (Intermediate)

Plan before you code

A project is just a bigger problem. The trick is to plan first. Write down three things: the inputs (what data comes in), the outputs (what answers must come out) and the steps in between. Each step usually becomes one small function.

Think of it like this: A tailor measures you, writes the numbers down and marks the cloth with chalk before cutting it. Cutting first and measuring later wastes cloth. Planning a program is the chalk mark: it costs a few minutes and saves hours of fixing.

Part	For our report card
Inputs	Each student: a name and marks in 5 subjects, each out of 100
Outputs	Total, percentage, grade, PASS or FAIL, class topper, class average
Steps	check marks, add them, find percentage, find grade, check pass, repeat for the class

Our grading scheme

Every school board publishes its own rules. For this project we use one simple scheme and write it down clearly, so the program and the people agree.

Percentage	Grade
90 and above	A
75 to below 90	B
60 to below 75	C
33 to below 60	D
below 33	F

Careful: Pass rule: a student passes only if EVERY subject is 33 or more. A student with 95 in four subjects and 20 in one subject fails, even though the percentage is high. In that case our report card shows grade F.

Step 1: check, total and percentage

We keep one student's marks in a dictionary: subject name to mark. The first function checks that every mark is between 0 and 100, because a typing mistake like 870 would spoil every answer after it.

python

def check_marks(marks):
    for subject, mark in marks.items():
        if not 0 <= mark <= 100:
            raise ValueError(f"{subject}: mark {mark} must be between 0 and 100")

def total(marks):
    check_marks(marks)
    return sum(marks.values())

def percentage(marks):
    max_total = len(marks) * 100
    return round(total(marks) / max_total * 100, 2)

marks = {"English": 78, "Hindi": 85, "Maths": 92, "Science": 88, "Social Science": 81}
print(total(marks))       # 424
print(percentage(marks))  # 84.8

Each function does one job. percentage() reuses total(), which reuses check_marks().

Step 2: grade and pass

python

def grade(percent):
    if percent >= 90:
        return "A"
    elif percent >= 75:
        return "B"
    elif percent >= 60:
        return "C"
    elif percent >= 33:
        return "D"
    return "F"

def has_passed(marks):
    return all(mark >= 33 for mark in marks.values())

print(grade(84.8))                                 # B
print(has_passed({"Maths": 95, "Hindi": 20}))      # False

The if/elif chain checks from the highest band down, so the first match is the right grade.

Step 3: the whole class

Now we join the pieces. report() builds one student's result as a dictionary. class_topper() uses max() with a key, and class_average() uses statistics.mean(). Here is the complete program in one place.

python

import statistics

def total(marks):
    return sum(marks.values())

def percentage(marks):
    return round(total(marks) / (len(marks) * 100) * 100, 2)

def grade(percent):
    for limit, letter in [(90, "A"), (75, "B"), (60, "C"), (33, "D")]:
        if percent >= limit:
            return letter
    return "F"

def has_passed(marks):
    return all(mark >= 33 for mark in marks.values())

def report(student):
    marks = student["marks"]
    passed = has_passed(marks)
    pct = percentage(marks)
    return {
        "name": student["name"],
        "total": total(marks),
        "percentage": pct,
        "grade": grade(pct) if passed else "F",
        "result": "PASS" if passed else "FAIL",
    }

def class_topper(students):
    best = max(students, key=lambda s: total(s["marks"]))
    return best["name"]

def class_average(students):
    return round(statistics.mean(percentage(s["marks"]) for s in students), 2)

students = [
    {"name": "Aarav", "marks": {"Eng": 78, "Hin": 85, "Mat": 92, "Sci": 88, "SSt": 81}},
    {"name": "Diya", "marks": {"Eng": 91, "Hin": 89, "Mat": 97, "Sci": 94, "SSt": 90}},
    {"name": "Kabir", "marks": {"Eng": 65, "Hin": 30, "Mat": 72, "Sci": 58, "SSt": 61}},
]
for s in students:
    print(report(s))
print("Topper:", class_topper(students))
print("Class average:", class_average(students))

Kabir has a good total but 30 in Hindi, so his result is FAIL with grade F.

Step 4: test with answers you already know

Testing means running your functions on inputs where you already know the right answer. Work a few out by hand, then let assert compare. Pay extra attention to the edges: exactly 33, exactly 90, and just below them. Bugs love edges.

python

def grade(percent):
    for limit, letter in [(90, "A"), (75, "B"), (60, "C"), (33, "D")]:
        if percent >= limit:
            return letter
    return "F"

assert grade(90) == "A", "exactly 90 is an A"
assert grade(89.99) == "B", "just below 90 is a B"
assert grade(33) == "D", "exactly 33 passes with D"
assert grade(32.99) == "F", "below 33 is F"
print("All grade tests passed")

If any assert is wrong, Python stops and shows its message.

Tip: Build one function, test it, then build the next. If you write all six functions first and then run them, you will not know which one has the bug.

Project: marks and grade calculator

Explanation

Plan before you code

Our grading scheme

Step 1: check, total and percentage

Step 2: grade and pass

Step 3: the whole class

Step 4: test with answers you already know

Watch the lesson

In real life: A class teacher at result time

Practice (0/3 done)

Quick quiz

Read more (free)