def price_index(price_of_product_x, price_of_product_y):
    """Return the price index of product X over product Y.

    Args:
        price_of_product_x (float): Price of product X.
        price_of_product_y (float): Price of product Y.

    Returns:
        price_index (float): Price of X / Price of Y
    """

    return (price_of_product_x / price_of_product_y) * 100