11 digit prime number generator

11_digit_prime_number.py

# Searches for 11 digits prime numbers
#
# This one is really slow for big numbers
# def isprime(num):
#     val = num-1L
#     while not val == 1L :
#         if num%val == 0L:
#             #print str(num) + "%" + str(val) + "==0"
#             return False
#         val = val -1L
#     return True


# prime numbers are only divisible by unity and themselves
# (1 is not considered a prime number by convention)
# source: http://www.daniweb.com/code/snippet216880.html 
def isprime(n):
    '''check if integer n is a prime'''
    # 0 and 1 are not primes
    if n < 2L:
        return False
    # 2 is the only even prime number
    if n == 2L:
        return True
    # all other even numbers are not primes
    if not n & 1L:
        return False
    # range starts with 3 and only needs to go up the squareroot of n
    # for all odd numbers
    for x in range(3L, long(n**0.5)+1L, 2L):
        if n % x == 0:
            return False
    return True        


def find_prime(start,r):
    """Finds prime numbers between start and end value."""
    primes = [val+start for val in range(r) if isprime(val+start)]
    for p in primes:
        print "Prime number = " + str(p)

find_prime(10000000000L,1000L)