ToDo_Notes.py

import os

class Todo:
    def __init__(self, filename="tasks.txt"):
        self.filename = filename
        self.tasks = []
        self.load_tasks()

    def load_tasks(self):
        if os.path.exists(self.filename):
            with open(self.filename, "r") as file:
                self.tasks = [line.strip() for line in file if line.strip()]

    def save_tasks(self):
        with open(self.filename, "w") as file:
            for task in self.tasks:
                file.write(task + "\n")

    def add_task(self, task):
        if task.strip() == "":
            print("Task cannot be empty!")
            return
        if task in self.tasks:
            print("Task already exists!")
            return
        self.tasks.append(task)
        self.save_tasks()
        print("Task added successfully!")

    def view_tasks(self):
        if not self.tasks:
            print("No tasks found!")
        else:
            print("\nYour Tasks:")
            for i, task in enumerate(self.tasks, 1):
                print(f"{i}. {task}")

    def delete_task(self, index):
        if 0 <= index < len(self.tasks):
            removed = self.tasks.pop(index)
            self.save_tasks()
            print(f"Task '{removed}' deleted!")
        else:
            print("Invalid task number!")

    def mark_complete(self, index):
        if 0 <= index < len(self.tasks):
            if "[DONE]" not in self.tasks[index]:
                self.tasks[index] += " [DONE]"
                self.save_tasks()
                print("Task marked as completed!")
            else:
                print("Task already completed!")
        else:
            print("Invalid task number!")



todo = Todo()

while True:
    print("\n--- To-Do Notes Builder ---")
    print("1. Add Task")
    print("2. View Tasks")
    print("3. Delete Task")
    print("4. Mark Task Complete")
    print("5. Exit")

    choice = input("Enter choice: ")

    if not choice.isdigit():
        print("Please enter a valid number!")
        continue

    choice = int(choice)

    if choice == 1:
        task = input("Enter task: ")
        todo.add_task(task)

    elif choice == 2:
        todo.view_tasks()

    elif choice == 3:
        todo.view_tasks()
        if todo.tasks:
            num = input("Enter task number to delete: ")
            if num.isdigit():
                todo.delete_task(int(num) - 1)
            else:
                print("Invalid input!")

    elif choice == 4:
        todo.view_tasks()
        if todo.tasks:
            num = input("Enter task number to mark complete: ")
            if num.isdigit():
                todo.mark_complete(int(num) - 1)
            else:
                print("Invalid input!")

    elif choice == 5:
        print("Exiting program.....")
        break

    else:
        print("Invalid choice!")