How to Build a Python Command-Line To-Do List App

Managing tasks efficiently is crucial for productivity. A command-line To-Do List app in Python is a simple yet powerful tool that allows you to keep track of your tasks directly from your terminal. This project is a great way to practice Python fundamentals, including file operations, user input handling, and list manipulations. Let’s build a command-line To-Do List app that enables users to add, view, complete, and delete tasks easily.

Features of the Command-Line To-Do List App

1. Add Tasks: Users can add new tasks to their list.

2. View Tasks: Display all tasks, showing their status (completed or pending).

3. Mark Tasks as Completed: Users can mark tasks as done.

4. Delete Tasks: Remove tasks from the list.

5. Save and Load Tasks: Tasks are saved to a file and loaded when the app starts, ensuring persistence.

Step-by-Step Implementation

Let’s walk through the steps to create this To-Do List app in Python.

Step 1: Setup Your Environment

First, make sure you have Python installed on your machine. No additional libraries are needed for this project, as we’ll use Python’s built-in functionalities.

Step 2: Define the Basic Structure

We’ll use a simple list to store tasks in memory and a text file (tasks.txt) to save tasks persistently. This file allows the app to remember tasks between sessions.

Here’s the basic structure of our Python script:

import os

# File to store tasks
TASK_FILE = "tasks.txt"

def load_tasks():
    """Load tasks from a file."""
    tasks = []
    if os.path.exists(TASK_FILE):
        with open(TASK_FILE, "r") as file:
            tasks = [line.strip() for line in file.readlines()]
    return tasks

def save_tasks(tasks):
    """Save tasks to a file."""
    with open(TASK_FILE, "w") as file:
        for task in tasks:
            file.write(f"{task}\n")

def add_task(tasks):
    """Add a new task to the list."""
    task = input("Enter the task description: ")
    tasks.append(task)
    print(f"Task '{task}' added.")

def view_tasks(tasks):
    """Display all tasks with their statuses."""
    if not tasks:
        print("No tasks available.")
    else:
        for index, task in enumerate(tasks, start=1):
            print(f"{index}. {task}")

def mark_task_complete(tasks):
    """Mark a task as completed."""
    view_tasks(tasks)
    try:
        task_number = int(input("Enter the task number to mark as complete: "))
        tasks[task_number - 1] = "[Completed] " + tasks[task_number - 1]
        print(f"Task {task_number} marked as complete.")
    except (ValueError, IndexError):
        print("Invalid task number.")

def delete_task(tasks):
    """Delete a task from the list."""
    view_tasks(tasks)
    try:
        task_number = int(input("Enter the task number to delete: "))
        task = tasks.pop(task_number - 1)
        print(f"Task '{task}' deleted.")
    except (ValueError, IndexError):
        print("Invalid task number.")

def main():
    """Main function to run the To-Do List app."""
    tasks = load_tasks()

    while True:
        print("\nTo-Do List App")
        print("1. View Tasks")
        print("2. Add Task")
        print("3. Mark Task as Completed")
        print("4. Delete Task")
        print("5. Exit")

        choice = input("Choose an option (1-5): ")

        if choice == "1":
            view_tasks(tasks)
        elif choice == "2":
            add_task(tasks)
            save_tasks(tasks)
        elif choice == "3":
            mark_task_complete(tasks)
            save_tasks(tasks)
        elif choice == "4":
            delete_task(tasks)
            save_tasks(tasks)
        elif choice == "5":
            print("Exiting the app. Goodbye!")
            break
        else:
            print("Invalid choice. Please try again.")

if __name__ == "__main__":
    main()

Step 3: Implement Core Functions

• load_tasks(): Reads tasks from the file and loads them into a list.

• save_tasks(tasks): Saves the current list of tasks to a file.

• add_task(tasks): Prompts the user to add a new task and appends it to the list.

• view_tasks(tasks): Displays all tasks with their status (pending or completed).

• mark_task_complete(tasks): Allows the user to mark a task as completed.

• delete_task(tasks): Deletes a selected task from the list.

• main(): Runs the app, handling user input to manage tasks.

Step 4: Running Your To-Do List App

To run your To-Do List app:

1. Save the script in a file named todo.py.

2. Open your terminal or command prompt.

3. Navigate to the directory where todo.py is located.

4. Run the script using Python:

    python todo.py
   

You will see a menu allowing you to view, add, complete, or delete tasks. Your tasks will be saved in tasks.txt for future sessions.