# Python : Find the Factorial of a Number

Tutorial by:Rizwan Abdullah      Date: 2016-06-16 00:51:13

The factorial of a number is the product of all the integers from 1 to that number. For example, the factorial of 6 (denoted as 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.

# 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 1

```
Enter a number: -2
Sorry, factorial does not exist for negative numbers
```

Output 2

```
Enter a number: 7
The factorial of 7 is 5040
```

Here, we take input from the user and 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.

## Python

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