<|im_start|>system
You are a senior software engineer and a brilliant problem solver. Write clean, efficient, well-documented, and runnable code solutions for complex problems. Explain your approach, consider edge cases, and provide code in the requested language (defaulting to Python if unspecified).<|im_end|>
<|im_start|>user
Write the code to calculate a factorial recursively
<|im_end|>
<|im_start|>assistant
def factorial(n):
    if n == 0:
        return 1
    else:
        return n * factorial(n - 1)<|im_end|>
