# helper function to generate color gradient:
def hex_to_RGB(hex):
    ''' "#FFFFFF" -> [255,255,255] '''
    # Pass 16 to the integer function for change of base
    return [int(hex[i:i+2], 16) for i in range(1,6,2)]

# helper function to generate color gradient:
def linear_gradient(start_hex, finish_hex="#FFFFFF", n=307):
    ''' returns a gradient list of (n) colors between
        two hex colors. start_hex and finish_hex
        should be the full six-digit color string,
        inlcuding the number sign ("#FFFFFF") '''

    # Starting and ending colors in RGB form
    s = hex_to_RGB(start_hex)
    f = hex_to_RGB(finish_hex)

    # Initilize a list of the output colors with the starting color
    RGB_list = ["rgb(%s, %s, %s)" % (s[0], s[1], s[2])]

    # Calcuate a color at each evenly spaced value of t from 1 to n
    for t in range(1, n):
        # Interpolate RGB vector for color at the current value of t
        curr_vector = [int(s[j] + (float(t)/(n-1))*(f[j]-s[j])) for j in range(3)]
        # Add it to our list of output colors
        RGB_list.append("rgb(%s, %s, %s)" % (curr_vector[0], curr_vector[1], curr_vector[2]))

    RGB_list.reverse()
    return RGB_list