Day 52 : Primes Numbers smaller than or equal to the Number

 

def SieveOfEratosthenes(n):

    primes = [True] * (n + 1)

    p = 2             # because p is the smallest prime

    while(p * p <= n):

        # if p is not marked as False, this it is a prime

        if(primes[p]) == True:

            # mark all the multiples of number as False

            for i in range(p * 2, n + 1, p):

                primes[i] = False

        p += 1        

    # printing all primes

    for i in range(2, n):

        if primes[i]:

            print(i)

if __name__ == '__main__':

    n=int(input("Enter a no to check all smaller prime numbers :"))

    SieveOfEratosthenes(n)

    #clcoding.com

Enter a no to check all smaller prime numbers :20
2
3
5
7
11
13
17
19