""" Sieve of Eratosthones The sieve of Eratosthenes is an algorithm used to find prime numbers, less than or equal to a given value. Illustration: https://upload.wikimedia.org/wikipedia/commons/b/b9/Sieve_of_Eratosthenes_animation.gif Reference: https://en.wikipedia.org/wiki/Sieve_of_Eratosthenes doctest provider: Bruno Simas Hadlich (https://github.com/brunohadlich) Also thanks Dmitry (https://github.com/LizardWizzard) for finding the problem """ import math def sieve(n): """ Returns a list with all prime numbers up to n. >>> sieve(50) [2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47] >>> sieve(25) [2, 3, 5, 7, 11, 13, 17, 19, 23] >>> sieve(10) [2, 3, 5, 7] >>> sieve(9) [2, 3, 5, 7] >>> sieve(2) [2] >>> sieve(1) [] """ l = [True] * (n + 1) # noqa: E741 prime = [] start = 2 end = int(math.sqrt(n)) while start <= end: # If start is a prime if l[start] is True: prime.append(start) # Set multiples of start be False for i in range(start * start, n + 1, start): if l[i] is True: l[i] = False start += 1 for j in range(end + 1, n + 1): if l[j] is True: prime.append(j) return prime if __name__ == "__main__": print(sieve(int(input("Enter n: ").strip())))