# Python Function to check Prime Number

In this example, we will learn whether the entered number is a prime number or not using a user-defined function.

A prime number is a number that is divisible by 1 and itself. The same principle we are going to explore in this example.

## Python Function to check the primary number [ Old method ]

def check_prime(n): flag = True for x in range(2, n//2): if n % x == 0: flag = False return flag if __name__ == "__main__": n = int(input('Enter any integer number : ')) result = check_prime(n) print("Prime Number " if (result) else '"Not prime Number')

Output of the above python program

rakesh@folio MINGW64 /e/python (master) $ python -u "e:\python\functions\check_prime.py" Enter any integer number : 16 "Not prime Number rakesh@folio MINGW64 /e/python (master) $ python -u "e:\python\functions\check_prime.py" Enter any integer number : 17 Prime Number rakesh@folio MINGW64 /e/python (master) $ python -u "e:\python\functions\check_prime.py" Enter any integer number : 1 Prime Number rakesh@folio MINGW64 /e/python (master) $ python -u "e:\python\functions\check_prime.py" Enter any integer number : 2 Prime Number

## A second and Most efficient method to check prime Number

from math import sqrt def prime_number(n): flag = True for x in range(2, int(sqrt(n))+1): if n % x == 0: flag = False return flag

Implementation of the above function to check Prime number. The above function tried to divide all the number between 2 and sqrt( ) of the number and this is the shortest method to check prime number.

if __name__ == "__main__": if(prime_number(12)): print('Prime Number') else: print('Not a prime Number')

The same function can be used to find out the prime number between two numbers.