[Python coding problem]: "I'm trying to write a function that calculates the factorial of a number but keep getting an error." [Error message]: "NameError: name 'factorial' is not defined" Output: It seems like you're encountering a NameError because Python doesn't recognize the name factorial. This typically happens when you try to use a variable or function that hasn't been defined yet. To solve this issue, you can either define the factorial function yourself or use the built-in math.factorial function. Here's how you can define the factorial function yourself: def factorial(n): if n == 0: return 1 else: return n * factorial(n-1) # Example usage: result = factorial(5) print(result) # Output will be 120 -------------------------------------------------------------------------- Alternatively, you can use the built-in math.factorial function: import math result = math.factorial(5) print(result) # Output will be 120 --------------------------------------------------------------------------- Both approaches will calculate the factorial of a given number. Choose the one that fits your needs best! Let me know if you need further clarification or assistance.