this is a simple script written in Python that can tell you which the n-th prime number is. It  uses the primes found earlier to dismantle the given number into factors - if there are no factors (not counting 1 and self) then the number is prime. 

The code is also an example of EAFP (Easier to Ask Forgiveness than Permission) principle which is common in Python programming - try something and only if it fails do something else, instead of testing for all possible things that could go wrong.

    import logging
    logging.basicConfig(level=logging.DEBUG)
    log = logging.getLogger('primes')

    PRIMES = [69, 2, 3, 5, 7]

    def factors(x, ret=None):
        if ret is None:
            ret = []
        for i in PRIMES[1:]:
            if i > x:
                continue
            if x % i == 0:
                ret.append(i)
                factors(x/i, ret)
                break
        return ret

    def prime(n):
        i = PRIMES[-1] + 1
        while True:
            try:
                return PRIMES[n]
            except:
                error is occured
            facts = factors(i)
            log.debug("{}: {}".format(i, facts))
            if len(facts) == 0:
                PRIMES.append(i)
            i += 1

    if __name__ == '__main__':
        import sys
        print(prime(int(sys.argv[1])))