# math.factorial() method with example in Python

Python math.factorial() method: Here, we are going to learn about the math.factorial() method with example in Python.
Submitted by IncludeHelp, on April 17, 2019

## Python math.factorial() method

math.factorial() method is a library method of math module, it is used to find the factorial of a given number, it accepts a positive integer number and returns the factorial of the number.

Note:

• The method accepts only integer (positive) value, if the value is either a negative or float – it returns "ValueError".
• If the number is 0 – its factorial will be 1.

Syntax of math.factorial() method:

```    math.factorial(n)
```

Parameter(s): n – a positive integer number.

Return value: int – it returns factorial of given number n.

Example:

```    Input:
a = 6

# function call
print(math.factorial(a))

Output:
720
```

### Python code to demonstrate example of math.factorial() method

```# Python code to demonstrate example of
# math.factorial() method

# importing math module
import math

# numbers
a = 0
b = 1
c = 6
d = 13

# printing factorial
print("factorial of ", a, " is = ", math.factorial(a))
print("factorial of ", b, " is = ", math.factorial(b))
print("factorial of ", c, " is = ", math.factorial(c))
print("factorial of ", d, " is = ", math.factorial(d))
```

Output

```factorial of  0  is =  1
factorial of  1  is =  1
factorial of  6  is =  720
factorial of  13  is =  6227020800
```

ValueError: factorial() not defined for negative values

If we try to find the factorial of a negative integer value – method will return this error.

```# Python code to demonstrate example of
# math.factorial() method

# importing math module
import math

# -ve integer
a = -5

print(math.factorial(a))
```

Output

```Traceback (most recent call last):
File "/home/main.py", line 10, in <module>
print(math.factorial(a))
ValueError: factorial() not defined for negative values
```

ValueError: factorial() only accepts integral values

If we try to find the factorial of a float value – method will return this error.

```# Python code to demonstrate example of
# math.factorial() method

# importing math module
import math

# -ve integer
a = 5.1

print(math.factorial(a))
```

Output

```Traceback (most recent call last):
File "/home/main.py", line 10, in <module>
print(math.factorial(a))
ValueError: factorial() only accepts integral values
```

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