is Prime Number

is_prime.py

def is_prime(x):
    """ Return True if 'x' is prime number, otherwise, return False """

    # positive numbers
    x = abs(int(x))

    # 0, 1 are not prime
    if x < 2:
        return False

    # 2 is primary number
    if x == 2:
        return True

    # even numbers are not prime
    if not x & 1:
        return False

    # range from 3 to only till square root of the target number
    for i in xrange(3, int(x**0.5) + 1, 2):
        if x % i == 0:
            return False

    return True