Tkinter program to create marksheet calculator

import tkinter as tk
from tkinter import ttk

class MarksheetCalculator:
    def __init__(self, root):
        self.root = root
        self.root.title("Marksheet Calculator")

        self.subjects = []
        self.marks = []

        self.create_widgets()

    def create_widgets(self):
        # Labels and Entry for Subjects and Marks
        subject_label = ttk.Label(self.root, text="Enter Subjects:")
        subject_label.grid(row=0, column=0, padx=10, pady=10, sticky=tk.W)

        self.subject_entry = ttk.Entry(self.root)
        self.subject_entry.grid(row=0, column=1, padx=10, pady=10)

        marks_label = ttk.Label(self.root, text="Enter Marks:")
        marks_label.grid(row=1, column=0, padx=10, pady=10, sticky=tk.W)

        self.marks_entry = ttk.Entry(self.root)
        self.marks_entry.grid(row=1, column=1, padx=10, pady=10)

        add_button = ttk.Button(self.root, text="Add Subject", command=self.add_subject)
        add_button.grid(row=1, column=2, padx=10, pady=10)

        # Display Subjects and Marks
        self.tree = ttk.Treeview(self.root, columns=("Subject", "Marks"), show="headings")
        self.tree.heading("Subject", text="Subject")
        self.tree.heading("Marks", text="Marks")
        self.tree.grid(row=2, column=0, columnspan=3, padx=10, pady=10)

        # Calculate Button
        calculate_button = ttk.Button(self.root, text="Calculate", command=self.calculate_result)
        calculate_button.grid(row=3, column=0, columnspan=3, pady=10)

        # Result Label
        self.result_label = ttk.Label(self.root, text="")
        self.result_label.grid(row=4, column=0, columnspan=3, pady=10)

    def add_subject(self):
        subject = self.subject_entry.get()
        marks = self.marks_entry.get()

        if subject and marks:
            self.subjects.append(subject)
            self.marks.append(int(marks))

            self.tree.insert("", "end", values=(subject, marks))

            # Clear entry fields
            self.subject_entry.delete(0, tk.END)
            self.marks_entry.delete(0, tk.END)

    def calculate_result(self):
        total_marks = sum(self.marks)
        average_marks = total_marks / len(self.marks)

        # Determine the grade based on the average
        if average_marks >= 90:
            grade = "A+"
        elif 80 <= average_marks < 90:
            grade = "A"
        elif 70 <= average_marks < 80:
            grade = "B"
        elif 60 <= average_marks < 70:
            grade = "C"
        elif 50 <= average_marks < 60:
            grade = "D"
        else:
            grade = "F"

        result_text = f"Total Marks: {total_marks}\nAverage Marks: {average_marks:.2f}\nGrade: {grade}"
        self.result_label.config(text=result_text)

# Create the main window
root = tk.Tk()

# Create the MarksheetCalculator instance
marksheet_calculator = MarksheetCalculator(root)

# Start the Tkinter event loop
root.mainloop()