Simple Fun #303: Prime Product

def prime_product(n):

    #beginning tests
    if n < 4:
        return 0

    #getting the list of primes inbetween n
    PRIMES = []
    for i in range(2,n):
        if is_prime(i):
            PRIMES.append(i)

    #decoy in case I need it later
    res = PRIMES
    pairs = set()
    for i in range(len(res)):
        if n - res[-(i+1)] in res:
            pairs.add((n-res[-(i+1)])*res[-(i+1)])
    if len(pairs) == 0:
        return 0
    return max(pairs)

#checks whether a given number is prime
def is_prime(i):
    for x in range(2,(i//2)+1):
        if i % x == 0:
            return False
    return True