isPrime.py

'''
    @author: TheRealMentor
    @date: 28/06/2019
'''

import math

def isPrime(A):
    #Check if A = 1
    if A == 1:
        return False
    #Check if A = 2 or 3
    if A == 2 or A == 3:
        return True
        
    #Check if A % i == 0 upto sqrt(n). This is trial division method.
    for i in range(2, int(math.sqrt(A))+1):
        if i < A and A % i == 0:
            return False
            
    return True

print(isPrime(7))
print(isPrime(19))
print(isPrime(21))