Prime Checker

from bisect import bisect_left

print('Generating 99,999 prime numbers... (Takes about 10 seconds)\n')

#-----------------------------------------------------------------------

def prime_list(n):
    sieve = [True] * n
    for i in xrange(3, int(n ** 0.5) + 1, 2):
        if sieve[i]:
            sieve[i * i::2 * i]=[False]*((n - i * i - 1) / (2 * i) + 1)
    return [2] + [i for i in xrange(3, n, 2) if sieve[i]]

biggest_prime = 1299721 # The 100,001st prime
second_to_biggest_prime = 1299709
list_of_primes = prime_list(biggest_prime)

def take_closest(the_list, num):
    pos = bisect_left(the_list, num)
    if pos == 0:
        return the_list[0]
    if pos == len(the_list):
        return the_list[-1]
    before = the_list[pos - 1]
    after = the_list[pos]
    if after - num < num - before:
        return after
    else:
        return before

def prime_info(num):

    if num == 1:
        return 0, 2, 'None', 2      # 2 is the first prime, No previous prime, next prime is 2
    if num == 2:
        return 1, 3, 'None', 3

    number_of_prime = 0
    nth_prime_number = 0
    previous_prime = 0
    next_prime = 0

    if num > 99999:
        nth_prime_number = 'Unavailable'
    else:
        nth_prime_number = list_of_primes[num - 1]

    if num < second_to_biggest_prime:   # The last prime before the biggest_prime

        if num in list_of_primes:
            number_of_prime = list_of_primes.index(num) + 1
            previous_prime = list_of_primes[number_of_prime - 2]
            next_prime = list_of_primes[number_of_prime]
        else:

            prime = take_closest(list_of_primes, num)

            if num > prime:
                previous_prime = prime
                index = list_of_primes.index(previous_prime) + 1
                next_prime = list_of_primes[index]
            else:
                next_prime = prime # Because the prime is greater than num
                index = list_of_primes.index(next_prime) - 1
                previous_prime = list_of_primes[index]

    else:

        previous_prime = 'Unavailable'
        next_prime = 'Unavailable'

    return number_of_prime, nth_prime_number, previous_prime, next_prime

#-----------------------------------------------------------------------

for i in range(1, 1000):
    prime_num, nth_prime, previous_prime, next_prime = prime_info(i)

    print('\n\nNumber: ' + str(i))
    print('Prime #' + str(i) + ' is ' + str(nth_prime))

    the_nth_prime = nth_prime
    two_sum = i + nth_prime

    print('The sum of these two numbers is ' + str(two_sum))

    prime_num, nth_prime, previous_prime, next_prime = prime_info(two_sum)

    if str(nth_prime) == 'Unavailable': exit()

    print('Prime #' + str(two_sum) + ' is ' + str(nth_prime))

    answer = nth_prime

    if len(str(answer)) > len(str(two_sum)):
        shortened = str(answer)[:len(str(two_sum))]

        if shortened == str(the_nth_prime):
            raw_input('                 Yes! ' + str(i) + ' self resolves!')

# The results for this program are 261, 262, and 263