app.py

import tkinter as tk
from tkinter import messagebox

class ToDoApp:
    def __init__(self, root):
        self.root = root
        self.root.title("ToDo Application")
        self.tasks = []

        self.frame = tk.Frame(root)
        self.frame.pack(pady=10)

        self.task_entry = tk.Entry(self.frame, width=40)
        self.task_entry.pack(side=tk.LEFT, padx=10)

        # Add Task button with black border
        self.add_button = tk.Button(self.frame, text="Add Task", font=("Arial Bold", 10), fg="red", 
                                    highlightbackground="black", highlightthickness=2, command=self.add_task)
        self.add_button.pack(side=tk.LEFT)

        self.task_listbox = tk.Listbox(root, width=50, height=10, selectmode=tk.SINGLE)
        self.task_listbox.pack(pady=10)

        # Create a frame to center the buttons
        self.button_frame = tk.Frame(root)
        self.button_frame.pack(pady=10)

        # Mark as Completed button with black border
        self.complete_button = tk.Button(self.button_frame, text="Mark as Completed", font=("Arial Bold", 10), fg="red", 
                                         highlightbackground="black", highlightthickness=2, command=self.mark_completed)
        self.complete_button.pack(side=tk.LEFT, padx=10)

        # Delete Task button with black border
        self.delete_button = tk.Button(self.button_frame, text="Delete Task", font=("Arial Bold", 10), fg="red", 
                                       highlightbackground="black", highlightthickness=2, command=self.delete_task)
        self.delete_button.pack(side=tk.LEFT)

    def add_task(self):
        task = self.task_entry.get()
        if task:
            self.tasks.append({"task": task, "completed": False})
            self.update_listbox()
            self.task_entry.delete(0, tk.END)
        else:
            messagebox.showwarning("Warning", "You must enter a task.")

    def update_listbox(self):
        self.task_listbox.delete(0, tk.END)
        for task in self.tasks:
            display_task = task["task"]
            if task["completed"]:
                display_task += " [Done]"
            self.task_listbox.insert(tk.END, display_task)

    def mark_completed(self):
        selected_task_index = self.task_listbox.curselection()
        if selected_task_index:
            index = selected_task_index[0]
            self.tasks[index]["completed"] = True
            self.update_listbox()
        else:
            messagebox.showwarning("Warning", "You must select a task to mark as completed.")

    def delete_task(self):
        selected_task_index = self.task_listbox.curselection()
        if selected_task_index:
            index = selected_task_index[0]
            del self.tasks[index]
            self.update_listbox()
        else:
            messagebox.showwarning("Warning", "You must select a task to delete.")

if __name__ == "__main__":
    root = tk.Tk()
    app = ToDoApp(root)
    root.mainloop()