Python program to find the factorial of a number using recursion

Question

A factorial of a number is the product of all the integers from 1 to that number.

For example, the factorial of 5 (denoted as 5!) is 1*2*3*4*5 = 120. The factorial of 0 is 1.

def recur_factorial(x):
 if x == 1:
 return 1
 else:
 return (x * recur_factorial(x - 1))
num = int(input("Enter number: "))
print("The factorial of", num, "is", recur_factorial(num))

So I would like to know whether I could make this program shorter and more efficient.

Also, I would like to know the advantages and disadvantages of recursion.

• Maarten Fabré: The factorial of 0 is 1. What does this code do for x==0?
• Justin: @MaartenFabré - I have edited my code to include your question above.
• Mast: Please do not update the code in your question to incorporate feedback from answers, doing so goes against the Question + Answer style of Code Review. This is not a forum where you should keep the most updated version in your question. Please see what you may and may not do after receiving answers .
• Mast: Once a question has an answer, leave the code in it alone. If the original code wasn't complete, please learn something from this for your next question.
• Justin: @MaartenFabré - if num == 0: print ("The factorial of 0 is 1")

Answer 1

Looking over your code, this is what I have for you:

• Your function can be turned into a one-liner
• You should use if __name__ == '__main__' to ensure you're not running this program externally.

Refactored Code:

def recur_factorial(x):
 return 1 if x == 1 else (x * recur_factorial(x - 1))
def main():
 num = int(input("Enter number: "))
 print("The factorial of", num, "is", recur_factorial(num))
if __name__ == '__main__':
 main()

You can read this StackOverflow question for more information about the advantages and disadvantages of recursion