Calculate difference in percentage between 2 hex colors

color_meter.py

"""
    This function is a direct Python 2.7+ translation of
    https://gist.github.com/mailtruck/2411659
    Will exit if executed without importing.
    --rautamiekka
"""

if __name__ == '__main__':
    from sys import exit as sysexit
    sysexit(1)

def color_meter(cwith, ccolor):
    if not cwith or len(str(cwith)) != 7 or not ccolor or len(str(ccolor)) != 7:
        raise ValueError(
            "Either of the parameters is not 7-digit integer."
        )

    _cwith  = int(str(cwith)[1:7]) if str(cwith)[0] == "#" else cwith
    _ccolor = int(str(ccolor)[1:7]) if str(ccolor)[0] == "#" else ccolor

    _r = int(str(_cwith)[0:2], 16)
    _g = int(str(_cwith)[2:4], 16)
    _b = int(str(_cwith)[4:6], 16)

    __r = int(str(_ccolor)[0:2], 16)
    __g = int(str(_ccolor)[2:4], 16)
    __b = int(str(_ccolor)[4:6], 16)

    p1 = _r / 255 * 100
    p2 = _g / 255 * 100
    p3 = _b / 255 * 100

    perc1 = int(
        round(
            (p1 + p2 + p3) / 3,
            0
        )
    )

    p1 = __r / 255 * 100
    p2 = __g / 255 * 100
    p3 = __b / 255 * 100

    perc2 = int(
        round(
            (p1 + p2 + p3) / 3,
            0
        )
    )

    return abs(perc1 - perc2)

I'm not that experienced with Python yet, however I found that running this code returns 0
print p1 inside definitioncode was also returning 0
I have placed floats around the r, g and b codes. like so:

    p1 = float(_r) / 255 * 100
    p2 = float(_g) / 255 * 100
    p3 = float(_b) / 255 * 100

    p1 = float(__r) / 255 * 100
    p2 = float(__g) / 255 * 100
    p3 = float(__b) / 255 * 100

now print p1 returns 135
print color_meter('#84D9A3','#144024') returns 11.89543