Added 'Sieve of Eratosthenes'

Prime Numbers/sieve_of_eratosthenes.py

@@ -0,0 +1,28 @@
+"""
+Python program to print all prime number smaller than or equal
+to the given input using Sieve of Eratosthenes.
+"""
+
+
+def sieve_of_eratosthenes(num):
+    # List to store whether a number is prime or not
+    prime = [True for i in range(num+1)]
+    p = 2
+    while (p*p <= num):
+        # If prime[p] is True, then p is a prime number
+        if (prime[p] == True):
+            # Update all multiples of Prime p
+            for i in range(p*p, num+1, p):
+                prime[i] = False
+        p += 1
+
+    # Print all prime numbers
+    for p in range(2, num+1):
+        if prime[p]:
+            print(p),
+
+
+if __name__ == '__main__':
+    num = int(input())
+    print("Following are the prime numbers smaller than or equal to {}".format(num))
+    sieve_of_eratosthenes(num)