Python Program to Find the Factorial of a Number

In this article, you'll learn to find the factorial of a number and display it.

To understand this example, you should have the knowledge of the following Python programming topics:

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

For example, the factorial of 6 is `1*2*3*4*5*6 = 720`. Factorial is not defined for negative numbers, and the factorial of zero is one, `0! = 1`.

Source Code

``````# 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)
``````

Output

```The factorial of 7 is 5040
```

Note: To test the program for a different number, change the value of `num`.

Here, the number whose factorial is to be found is stored in `num`, and we check if the number is negative, zero or positive using `if...elif...else` statement. If the number is positive, we use `for` loop and `range()` function to calculate the factorial.