Factorial Calculation in Python

# Introduction

In this project, you will learn how to calculate the factorial of a non-negative integer. The factorial of a positive integer is the product of all positive integers less than or equal to it, and the factorial of 0 is 1.

## 👀 Preview

$ python factorial.py
2! = 1 * 2 = 2
8! = 1 * 2 * 3 * 4 * 5 * 6 * 7 * 8 = 40320

## 🎯 Tasks

In this project, you will learn:

- How to create a `factorial.py` file in the `~/project` directory
- How to implement the `factorial` function to calculate the factorial of a non-negative integer
- How to handle negative inputs by raising a `ValueError` and display a prompt saying "Please enter a non-negative integer"

## 🏆 Achievements

After completing this project, you will be able to:

- Understand the concept of factorial and how to calculate it
- Write a Python function to calculate the factorial of a non-negative integer
- Handle input errors and display appropriate error messages
- Apply your knowledge of Python programming to solve a real-world problem