Reverse Check

pi = ''

with open('/path/to/pi.txt') as the_file: pi = the_file.read()

pi = pi[2:]     # If your Pi file starts with "3."

pi_len = len(pi)

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

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]]

print('Generating prime numbers...\n')

biggest_prime = 373587883 # Prime #20,000,000
list_of_primes = prime_list(biggest_prime)

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

for i, prime in enumerate(list_of_primes):
    if prime > pi_len: exit()

    num = i + 1

    if num % 10 != 0: continue

    amount = 10 ** len(str(num))
    remainder = amount - num
    back_r = str(remainder)[::-1]
    digits = pi[:prime]

    if digits.endswith(back_r):
        print('Prime: #' + str(num) + ' is ' + str(prime))
        print('Amount: ' + str(amount))
        print('Calculation: ' + str(amount) + ' - ' + str(num) + ' = ' + str(remainder))
        print('Number we are looking for backwards: ' + str(back_r) + '\n\n')
        #raw_input()