VERY BAD ALGORITHM AND CODE!

#!/usr/bin/python

from random import randint
from random import randrange

mp = 13
tries = 100
startlength = 1
sievesize = 100
k = 5

def pp(n, k):
    for p in primes:
        if n < p * p:
            return True
        if n % p == 0:
            return False
    (r, s) = (0, n - 1)
    while s % 2 == 0:
        r += 1
        s //= 2
    for _ in range(k):
        a = randrange(2, n - 1)
        x = pow(a, s, n)
        if x == 1 or x == n - 1:
            continue
        for _ in range(r - 1):
            x = pow(x, 2, n)
            if x == n - 1:
                break
        else:
            return False
    return True

def sieve(n):
    multiples = set()
    for i in range(2, n + 1):
        if i not in multiples:
            yield i
            multiples.update(range(i * i, n + 1, i))

if mp > 2 and mp <= 49:
    with open(str(mp)) as f:
        data = f.read()
    primes = list(sieve(sievesize))
    print 'mp:', mp, '  tries:', tries, '  mp length:', len(data), '  start length:', startlength, '  primes in sieve:', len(primes)
    print
    for y in range(int(startlength), len(data)):
        length = int(y)
        flag = False
        counter = 0
        while flag == False:
            counter += 1
            start = randint(0, len(data) - length)
            candidate = int(data[start:start + length])
            if len(str(candidate)) == length:
                if pp(candidate, k) == True:
                    print
                    print
                    print 'mp:', mp, '  tries:', tries, '  mp length:', len(data), '  result length:', length, '  result:', candidate
                    print
                    flag = True
            if counter == tries:
                print y,
                break
    print