How to write a program converting rgb to cmyk in python

rgb_scale = 255

cmyk_scale = 100

def rgb_to_cmyk(r,g,b):

if (r == 0) and (g == 0) and (b == 0):

return 0, 0, 0, cmyk_scale

# rgb [0,255] -> cmy [0,1]

c = 1 - r / float(rgb_scale)

m = 1 - g / float(rgb_scale)

y = 1 - b / float(rgb_scale)

min_cmy = min(c, m, y)

c = (c - min_cmy)

m = (m - min_cmy)

y = (y - min_cmy)

k = min_cmy

return c*cmyk_scale, m*cmyk_scale, y*cmyk_scale, k*cmyk_scale

def cmyk_to_rgb(c,m,y,k):

r = rgb_scale*(1.0-(c+k)/float(cmyk_scale))

g = rgb_scale*(1.0-(m+k)/float(cmyk_scale))

b = rgb_scale*(1.0-(y+k)/float(cmyk_scale))

return r,g,b