Tkinter, notepad. This script includes the core features: a text area, a menu bar (File/Edit/Help), and basic file operations (Open, Save, Exit).

notepad.py

import tkinter as tk
from tkinter import filedialog, messagebox

class Notepad:
    def __init__(self, root):
        self.root = root
        self.root.title("Untitled - Notepad Clone")
        self.root.geometry("800x600")

        # Create the main text area
        self.textarea = tk.Text(self.root, undo=True, font=("Consolas", 11))
        self.textarea.pack(fill=tk.BOTH, expand=True)

        # Create the Menu Bar
        self.menubar = tk.Menu(self.root)
        self.root.config(menu=self.menubar)

        # File Menu
        self.file_menu = tk.Menu(self.menubar, tearoff=0)
        self.menubar.add_cascade(label="File", menu=self.file_menu)
        self.file_menu.add_command(label="New", command=self.new_file)
        self.file_menu.add_command(label="Open...", command=self.open_file)
        self.file_menu.add_command(label="Save", command=self.save_file)
        self.file_menu.add_separator()
        self.file_menu.add_command(label="Exit", command=self.root.quit)

        # Edit Menu
        self.edit_menu = tk.Menu(self.menubar, tearoff=0)
        self.menubar.add_cascade(label="Edit", menu=self.edit_menu)
        self.edit_menu.add_command(label="Undo", command=self.textarea.edit_undo)
        self.edit_menu.add_command(label="Redo", command=self.textarea.edit_redo)
        self.edit_menu.add_separator()
        self.edit_menu.add_command(label="Cut", command=lambda: self.root.focus_get().event_generate("<<Cut>>"))
        self.edit_menu.add_command(label="Copy", command=lambda: self.root.focus_get().event_generate("<<Copy>>"))
        self.edit_menu.add_command(label="Paste", command=lambda: self.root.focus_get().event_generate("<<Paste>>"))

        # Help Menu
        self.help_menu = tk.Menu(self.menubar, tearoff=0)
        self.menubar.add_cascade(label="Help", menu=self.help_menu)
        self.help_menu.add_command(label="About Notepad", command=self.show_about)

        self.file_path = None

    def new_file(self):
        self.root.title("Untitled - Notepad Clone")
        self.textarea.delete(1.0, tk.END)
        self.file_path = None

    def open_file(self):
        self.file_path = filedialog.askopenfilename(defaultextension=".txt", 
                                                    filetypes=[("Text Documents", "*.txt"), ("All Files", "*.*")])
        if self.file_path:
            self.root.title(f"{self.file_path} - Notepad Clone")
            self.textarea.delete(1.0, tk.END)
            with open(self.file_path, "r") as file:
                self.textarea.insert(1.0, file.read())

    def save_file(self):
        if self.file_path is None:
            self.file_path = filedialog.asksaveasfilename(initialfile='Untitled.txt', 
                                                          defaultextension=".txt", 
                                                          filetypes=[("Text Documents", "*.txt"), ("All Files", "*.*")])
        
        if self.file_path:
            with open(self.file_path, "w") as file:
                file.write(self.textarea.get(1.0, tk.END))
            self.root.title(f"{self.file_path} - Notepad Clone")

    def show_about(self):
        messagebox.showinfo("About", "This is a simple Notepad clone built with Python and Tkinter.")

if __name__ == "__main__":
    root = tk.Tk()
    notepad = Notepad(root)
    root.mainloop()