- Python Basic Programs
- Python Program Examples
- Python Print Hello World
- Python Get Input from User
- Python Add Two Numbers
- Add Subtract Multiply Divide
- Python Check Even or Odd
- Python Check Prime or Not
- Python Check Alphabet or Not
- Python Check Vowel or Not
- Python Check Leap Year or Not
- Check Reverse equal Original
- Check Positive Negative Zero
- Python Check Armstrong or Not
- Python Check Palindrome or Not
- Python Check Perfect Number
- Python Find Reverse of Number
- Python Count Digits in Number
- Python Add Digits of Number
- Sum of First and Last Digits
- Python Product of Mid Digits
- Sum of Squares of Digits
- Interchange Digits of Number
- Python Sum of n Numbers
- Python Print ASCII Values
- Python Swap Two Numbers
- Python Swap Two Variables
- Python Fahrenheit to Celsius
- Python Celsius to Fahrenheit
- Python Display Calendar
- Python Days into Years, Weeks
- Find Largest of Two Number
- Find Largest of Three Number
- Python Print Fibonacci Series
- Generate Armstrong Numbers
- Python Make Simple Calculator
- Python Add Binary Numbers
- Binary Number Multiplication
- Python Mathematical Programs
- Find Sum of Natural Numbers
- Find Average of n Numbers
- Python Print Multiplication Table
- Print Table using Recursion
- Python Find Average Percentage
- Python Find Grade of Student
- Find Square Root of Number
- Python Print Prime Numbers
- Find Numbers Divisible by
- Python Find Factors of Number
- Python Find Factorial of a Number
- Python Find HCF & LCM
- Python Kilometres to Miles
- Python Find Area of Square
- Python Find Area of Rectangle
- Python Find Area of Triangle
- Python Find Area of Circle
- Python Find Perimeter of Square
- Find Perimeter of Rectangle
- Python Find Perimeter of Triangle
- Find Circumference of Circle
- Python Simple Interest
- Python Solve Quadratic Equation
- Python Different Set of Operations
- Python Display Powers of 2
- Python Find nCr & nPr
- Python Pattern Programs
- Python Print Pattern Programs
- Python Print Diamond Pattern
- Python Print Floyd's Triangle
- Python Print Pascal's Triangle
- Python List Programs
- Python Count Even/Odd in List
- Python Positive/Negative in List
- Python Even Numbers in List
- Python Odd Numbers in List
- Python Sum of Elements in List
- Sum of Odd/Even Numbers
- Python Element at Even Position
- Python Element at Odd Position
- Python Search Element in List
- Python Largest Number in List
- Python Smallest Number in List
- Python Second Largest in List
- Python Second Smallest in List
- Python Insert Element in List
- Python Delete Element from List
- Python Multiply Numbers in List
- Swap Two Elements in List
- Python 1D Array Program
- Python Linear Search
- Python Binary Search
- Python Insertion Sort
- Python Bubble Sort
- Python Selection Sort
- Remove Duplicates from List
- Python Reverse a List
- Python Merge Two List
- Python Copy a List
- Python Conversion Programs
- Python Decimal to Binary
- Python Decimal to Octal
- Python Decimal to Hexadecimal
- Python Binary to Decimal
- Python Binary to Octal
- Python Binary to Hexadecimal
- Python Octal to Decimal
- Python Octal to Binary
- Python Octal to Hexadecimal
- Python Hexadecimal to Decimal
- Python Hexadecimal to Binary
- Python Hexadecimal to Octal
- Python Matrix Programs
- Python Add Two Matrices
- Python Subtract Two Matrices
- Python Transpose Matrix
- Python Multiply Matrices
- Python String Programs
- Python Print String
- Python Find Length of String
- Python Compare Two Strings
- Python Copy String
- Python Concatenate String
- Python Reverse a String
- Python Swap Two Strings
- Python Uppercase to Lowercase
- Python Lowercase to Uppercase
- Python Check Substring in String
- Python Count Character in String
- Count Repeated Characters
- Python Count Word in Sentence
- Python Count Each Vowels
- Python Capitalize Character
- Python Capitalize Word in String
- Python Smallest/Largest Word
- Remove Spaces from String
- Remove Duplicate Character
- Remove Vowels from String
- Remove Punctuation from String
- Python Remove Word in String
- Python Remove Duplicate Words
- WhiteSpace to Hyphens
- Replace Vowels with Character
- Replace Character in String
- Python Sort String in Alphabetical
- Sort Word in Alphabetical Order
- Extract Number from String
- Python Check Anagram Strings
- Python File Programs
- Python Read a File
- Python Write to File
- Python Append Text to File
- Python Copy Files
- Python Merge Two Files
- Python Counts Characters in File
- Python Count Words in File
- Python File Content in Reverse
- Python Lines Contains String
- Python Delete Line from File
- Python Capitalize Word in File
- Python Replace Text in File
- Replace Specific Line in File
- Python Find Size of File
- Python List Files in Directory
- Python Delete Files
- Python Misc Programs
- Python Reverse a Tuple
- Python Merge Two Dictionary
- Python bytes to String
- Python bytearray to String
- Generate Random Numbers
- Python Print Address of Variable
- Python Print Date and Time
- Python Get IP Address
- Python Shutdown/Restart PC
- Python Tutorial
- Python Tutorial
- Give Online Test
- All Test List
- Python Online Test

# Python Program to Find Factorial of a Number

In this article, I've created some programs in Python, that find and prints factorial of a given number by user at run-time. Here are the list of approaches used:

- Find Factorial of a Number using
**while**Loop - Using
**for**Loop - Using user-defined Function
- Using Recursion
- Using Class

Before creating these programs, let's remind about factorial formula, that is:

n! = (n)*(n-1)*(n-2)*...*3*2*1

Here **n** indicates a number of which, the factorial is going to find. The **!** (exclamation) indicates
factorial. So **n!** can be called as **n factorial**. For example, **5!** can be calculated as:

5! = 5*4*3*2*1 = 120

## Find Factorial using while Loop

To find factorial of any number in Python, you have to ask from user to enter the number, then find and print its factorial as per the formula given above, like shown in the program given below.

The question is, **write a Python program to find factorial of a given number using while loop**. Here is its answer:

print("Enter the Number: ") num = int(input()) fact = 1 i = 1 while i<=num: fact = fact*i i = i+1 print("\nFactorial =", fact)

Here is the initial output produced by this Python program:

Now supply the input say **5** as number and press `ENTER`

key to find its factorial like shown in the snapshot given below:

The dry run of above program with user input **5** goes like:

- Initial values,
**num=5**(entered by user),**fact=1**,**i=1** - Now the execution of
**while**loop begins - That is, the condition
**i<=num**or**1<=5**evaluates to be true, therefore program flow goes inside the loop (inside its body) - Inside the loop,
**fact*i**or**1*1**or**1**gets initialized to**fact**. And the value of**i**gets incremented by 1. So**i=2** - Again the condition
**i<=num**or**2<=5**evaluates to be true, therefore again**fact*i**or**1*2**or**2**gets initialized to**fact**. So**fact=2** - And
**i+1**or**2+1**or**3**gets initialized to**i**. So**i=3** - Again the condition,
**i<=num**or**3<=5**evaluates to be true, therefore program flow again goes inside the loop and executes its two statements. This process continues until the condition evaluates to be false - In this way, after exiting from the loop, the variable
**fact**holds the factorial value of a number stored in**num**variable - So just print the value of
**fact**as factorial of a given number

## Find Factorial using for Loop

This program does the same job as of previous program, but using **for** loop, instead of **while**. The **try-except** is
used in this program to handle with invalid inputs entered by user. And **end** is used to skip inserting an automatic newline.

print("Enter a Number: ", end="") try: num = int(input()) fact = 1 for i in range(1, num+1): fact = fact*i print("\nFactorial of", num, "=", fact) except ValueError: print("\nInvalid Input!")

Here is its sample run with same user input as of previous program:

In above program, the following code:

for i in range(1, num+1):

is applied to execute the following statement:

fact = fact*i

**num** number of times with value of **i** from 1 to **num**'s value.

## Find Factorial using Function

This program is created using a user-defined function named **findFact()**. This function receives a value as its
argument, then find and returns its factorial.

def findFact(n): f = 1 for i in range(1, n+1): f = f*i return f print("Enter a Number: ", end="") try: num = int(input()) fact = findFact(num) print("\nFactorial of", num, "=", fact) except ValueError: print("\nInvalid Input!")

This program produces same output as of previous program:

## Find Factorial using Recursion

The following program is created using a recursive function named **findFact()**. This function calls itself until
the value of its argument becomes equal to **1**.

def findFact(n): if n==1: return n else: return n*findFact(n-1) print("Enter a Number: ", end="") try: num = int(input()) fact = findFact(num) print("\nFactorial of", num, "=", fact) except ValueError: print("\nInvalid Input!")

## Find Factorial using Class

This is the last program to find and print factorial of a number entered by user, created using a class named **CodesCracker**. An
object **ob** is created of this class to access its member function (findFact()) using **dot (.)** operator:

class CodesCracker: def findFact(self, n): f = 1 for i in range(1, n + 1): f = f * i return f print("Enter a Number: ", end="") num = int(input()) ob = CodesCracker() print("\nFactorial of", num, "=", ob.findFact(num))

#### Same Program in Other Languages

« Previous Program Next Program »

Follow/Like Us on Facebook

Subscribe Us on YouTube