task 1

import tkinter as tk
from tkinter import messagebox

class TodoApp:
    def __init__(self, root):
        self.root = root
        self.root.title("To-Do List")

        self.tasks = []

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

        self.task_listbox = tk.Listbox(
            self.task_frame, 
            width=50, 
            height=10, 
            selectmode=tk.SINGLE
        )
        self.task_listbox.pack(side=tk.LEFT, fill=tk.BOTH)

        self.scrollbar = tk.Scrollbar(
            self.task_frame, 
            orient=tk.VERTICAL, 
            command=self.task_listbox.yview
        )
        self.scrollbar.pack(side=tk.RIGHT, fill=tk.Y)
        self.task_listbox.config(yscrollcommand=self.scrollbar.set)

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

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

        self.add_button = tk.Button(
            self.entry_frame, 
            text="Add Task", 
            width=10, 
            bg="green", 
            fg="white",
            command=self.add_task
        )
        self.add_button.pack(side=tk.LEFT)

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

        self.delete_button = tk.Button(
            self.button_frame, 
            text="Delete Task", 
            width=10, 
            bg="red", 
            fg="white",
            command=self.delete_task
        )
        self.delete_button.pack(side=tk.LEFT, padx=10)

        self.mark_button = tk.Button(
            self.button_frame, 
            text="Mark Completed", 
            width=15, 
            command=self.mark_completed
        )
        self.mark_button.pack(side=tk.LEFT, padx=10)

    def add_task(self):
        task = self.task_entry.get()
        if task != "":
            self.tasks.append(task)
            self.task_listbox.insert(tk.END, task)
            self.task_entry.delete(0, tk.END)
        else:
            messagebox.showwarning("Warning", "You must enter a task.")

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

    def mark_completed(self):
        selected_task_index = self.task_listbox.curselection()
        if selected_task_index:
            task_index = selected_task_index[0]
            task = self.tasks[task_index]
            self.tasks[task_index] = f"{task} (Completed)"
            self.task_listbox.delete(task_index)
            self.task_listbox.insert(task_index, self.tasks[task_index])
        else:
            messagebox.showwarning("Warning", "You must select a task to mark as completed.")

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