Python Factorial Program

This is a basic Python program which helps school and college students to improve their knowledge in Python.

If you don’t know what is factorial, here is a small explanation,

Multiplying given integer with the sequence of descending positive integers is called factorial.  For example,

5! is 5 x 4 x 3 x 2 x 1 = 120
So the value of 5! is 120

We can also find the values in the reverse way ie.,
5! is 1 x 2 x 3 x 4 x 5 = 120

In this program we are going to follow the above second method to find the value of the n! (n factorial)

Now, lets see the Python Factorial Program here:

print ("Enter Number to calculate Factorial: ")

#get the input
n = int(input())
fact = 1

print ("Factorial of", n, "is:")
#loop range from 1 to n
for i in range(1, n + 1):
    fact = fact * i
    print (fact)

This code works in both the Python 2 and Python 3 versions.

Let’s see the CGI version aka Python web version of this program:

#!/usr/bin/python
print "Content-type: text/html\n\n";

# Import modules for CGI handling 
import cgi, cgitb 

print '''
<html>
<head><title>Python CGI program to find n! (n factorial)</title></head>
<body>
    <h3>Web Based Factorial Python script to find n!  - <a href="http://www.tutorialsmade.com/">Tutorialsmade.com</a></h3>
    <form action="" method="post">
        <label>Enter Number to calculate Factorial:<label>
        <input type="text" name="n" />
        <input type="submit" value="Submit" />
    </form><br /><br />
</body>
</html>
'''

# Create instance of FieldStorage 
form = cgi.FieldStorage() 

#get the input
n = form.getvalue('n')

if(n):
	#type case string to int
	n = int(n)
	fact = 1
	print "Factorial of", n, "is:", "<br>"
	#loop range from 1 to n
	for i in range(1, n + 1):
		fact = fact * i
		print fact,"<br>"

It’s same as the normal Python application program but the only difference is the extra Form added in this script.

Here is the demo of the above script: