Scale a Hex color in Python

scale_hex.py

# Adapted from Thadeus Burgess' Python 2 code 
# http://thadeusb.com/weblog/2010/10/10/python_scale_hex_color/

def clamp(val, minimum=0, maximum=255):
    if val < minimum:
        return minimum
    if val > maximum:
        return maximum
    return val

def colorscale(hexstr, scalefactor):
    """
    Scales a hex string by ``scalefactor``. Returns scaled hex string.

    To darken the color, use a float value between 0 and 1.
    To brighten the color, use a float value greater than 1.

    >>> colorscale("#DF3C3C", .5)
    #701E1E
    >>> colorscale("#52D24F", 1.6)
    #83FF7E
    >>> colorscale("#4F75D2", 1)
    #4F75D2
    """

    hexstr = hexstr.strip('#')

    if scalefactor < 0 or len(hexstr) != 6:
        return hexstr

    r, g, b = int(hexstr[:2], 16), int(hexstr[2:4], 16), int(hexstr[4:], 16)

    r = clamp(int(round(r * scalefactor)))
    g = clamp(int(round(g * scalefactor)))
    b = clamp(int(round(b * scalefactor)))

    return '#{}{}{}'.format(hex(r)[2:], hex(g)[2:], hex(b)[2:]).upper()