# asweigart/codebreaker

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 # Prime Number Sieve # http://inventwithpython.com/hacking (BSD Licensed) import math def isPrime(num): # Returns True if num is a prime number, otherwise False. # Note: Generally, isPrime() is slower than primeSieve(). # all numbers less than 2 are not prime if num < 2: return False # see if num is divisible by any number up to the square root of num for i in range(2, int(math.sqrt(num)) + 1): if num % i == 0: return False return True def primeSieve(sieveSize): # Returns a list of prime numbers calculated using # the Sieve of Eratosthenes algorithm. sieve = [True] * sieveSize sieve[0] = False # zero and one are not prime numbers sieve[1] = False # create the sieve for i in range(2, int(math.sqrt(sieveSize)) + 1): pointer = i * 2 while pointer < sieveSize: sieve[pointer] = False pointer += i # compile the list of primes primes = [] for i in range(sieveSize): if sieve[i] == True: primes.append(i) return primes
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