Python Program to Find the Factorial of a Number

[elisahill]

# Python program to find the factorial of a number provided by the user.

# change the value for a different result
num = 7

# To take input from the user
#num = int(input("Enter a number: "))

factorial = 1

# check if the number is negative, positive or zero
if num < 0:
   print("Sorry, factorial does not exist for negative numbers")
elif num == 0:
   print("The factorial of 0 is 1")
else:
   for i in range(1,num + 1):
       factorial = factorial*i
   print("The factorial of",num,"is",factorial)

Yoriz write Nov-21-2022, 09:24 AM:
Please post all code, output and errors (in their entirety) between their respective tags. Refer to BBCode help topic on how to post. Use the "Preview Post" button to make sure the code is presented as you expect before hitting the "Post Reply/Thread" button.

[Larz60+]

Line 17, change both '1' to 'i' line 17

[DeaD_EyE]

Use a function:

def factorial(num):
    factorial = 1

    if num < 0:
        print("Sorry, factorial does not exist for negative numbers")
    else:
        for i in range(1, num + 1):
            factorial *= i
        print("The factorial of", num, "is", factorial)

With math.factorial it's easier:

def factorial(num):
    if num < 0:
        print("Sorry, factorial does not exist for negative numbers")
    else:
        print("The factorial of", num, "is", math.factorial(num))

A function that annoys the user until he has entered an integer:

import math


def factorial():
    max_value = 2_000

    while True:
        user_input = input("Factorial of: ")

        try:
            value = int(user_input)
        except ValueError:
            print("A valid integer is required")
            continue

        if value < 0:
            print("Negative integers are not allowed")
            continue

        if value > max_value:
            print(f"Integer is bigger than {max_value}")
            continue

        break

    print(math.factorial(value))