fill in the gaps...
while True:
    time.sleep(2)
    new_price = get_true_price()
    sec_since_update += 2
    if abs(new_price - last_price) / last_price > (SPREAD / 3):
        log("Price moved  -  old:  %f   new:  %f" % (last_price, new_price))
        log("Seconds since previous update:  %d" % sec_since_update)
        client.cancel_all_orders("USD", SYMBOL)
        client.wait_for_block()
        usd_balance = client.get_balance("USD")
        btsx_balance = client.get_balance(SYMBOL)
        client.submit_bid(0.3*(usd_balance * new_price), SYMBOL, new_price * (1+SPREAD), "USD")
        client.submit_ask(0.3*btsx_balance, SYMBOL, new_price * (1-SPREAD), "USD")
        last_price = new_price