In this article, we would discuss how to **find factorial of a number** through Python program. First, we would illustrate it using **for loop and if-else statement**. Subsequently, to get the desired outcome we will use **factorial function** defined in **math module**.

We can calculate factorial value of only positive integers. Therefore, we would write appropriate code while using **for loop** and **if-else statement**. On the other hand, factorial function itself takes care of such anomalies (i.e. negative values).

Factorial of a number (n) is the product of all numbers from 1 to n.

For instance, factorial of 7 is –

In addition to, factorial of 0 is 1.

##### Find factorial using for loop and if-else statement

#Ask the user to input a number x=int(input("Enter a number: ")) fact=1 if x==0: print("The factorial of 0 is 1") elif x<0: print("The factorial exists only for positive integers") else: for i in range(1,x+1): fact=fact*i print("The factorial of ",x," is", fact)

Herein, variable **x** stores the value entered by user. Thereafter, it is checked for three conditions. First two conditions are self-explanatory. But, if the value entered by user is greater than 0 then it invokes **for loop**. The range of **for loop** here is **1 to x**. And, the **fact** variable stores the resultant value. Initial value of **fact** variable is **1**.

So, if the user enters **x** as **7**. Then, for loop runs for **i = 1 to 7** and **fact** variable value gets updated every time. When the **for loop** has run its course, we get the result **5040**.

##### Find factorial using factorial() function

Alternately, we can use **factorial()** function to get the desired outcome. For that, we need to first **import math module**.

#Ask the user to input a number x=int(input("Enter a number: ")) import math fact=math.factorial(x) print("The factorial of ",x," is", fact)

We cannot use functions provided through** math module** with complex numbers. To use factorial function, we have used **math.factorial()** and stored the resultant value in variable **fact**. The program would work for all positive integer values. It will return output as 1 for 0!. But, for negative values, it will throw a **ValueError** exception –

ValueError: factorial() not defined for negative values

**In conclusion**, we have discussed how to find factorial of a number through Python program.

**Additional Info:**

It is necessary to properly use indentation in Python. Otherwise, it may throw **IndentationError** exception.