def ticks_difference(price_1, price_2):
price_1_index = PRICES.index(as_dec(price_1))<EOL>price_2_index = PRICES.index(as_dec(price_2))<EOL>return abs(price_1_index - price_2_index)<EOL>
Returns the absolute difference in terms of "ticks" (i.e. individual
    price increments) between two Betfair prices.

    :param float price_1: An exact, valid Betfair price
    :param float price_2: An exact, valid Betfair price
    :returns: The absolute value of the difference between the prices in "ticks"
    :rtype: int