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

[Managing tasks](https://bytescrum.com/) efficiently is crucial for productivity. A command-line To-Do List app in [Python](https://blog.bytescrum.com/series/python-series) 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](https://blog.bytescrum.com/how-to-setup-your-python-development-environment-a-step-by-step-tutorial) 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:

```python
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:
    
    ```bash
    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.

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1724653735088/3ea16eaf-a9c3-4563-9fa0-78af10bc09ec.png align="right")

<details data-node-type="hn-details-summary"><summary>Conclusion</summary><div data-type="detailsContent">Building a command-line To-Do List app in Python is a fantastic way to enhance your programming skills. This project covers fundamental concepts such as file I/O, list manipulations, and user input handling. You can expand this project further by adding features like setting due dates, categorizing tasks, or integrating it with a web-based front end. Happy coding!</div></details>