Conversion of wavelength in nanometers to RGB in Python

I've been recently doing some calibration/benchmark/demonstration measurements of spectra on an instrument I'm building and thought that it would be cool to visualize the spectra so that you could actually see them in colour. I've also never been able to memorize what colour which wavelength was, so this could even be a self-education project. In other words, the task was to transform wavelength data in nanometers into RGB data.

A short Google search turned up some very informative sites and among them was the algorithm for nanometer to RGB conversion. What seems to be the oldest search result is a conversion algorithm written by Dan Bruton in FORTRAN. You may also be interested in the Color Science site from the same author. As I was a bit confused by the FORTRAN code, I also used what appears to be a translation of this code into C#. I know C# about as much as FORTRAN but the syntax was more understandable to me. My only contribution was a literal translation of the algorithm into Python.

The function takes a value in nanometers and returns a list of [R, G, B] values. Although a PIL putpixel function requires a tuple, I found a list more flexible in case you want to change the values e.g. according to measured intensity. So, here is the code:

def wav2RGB(wavelength):
    w = int(wavelength)

    # colour
    if w >= 380 and w < 440:
        R = -(w - 440.) / (440. - 350.)
        G = 0.0
        B = 1.0
    elif w >= 440 and w < 490:
        R = 0.0
        G = (w - 440.) / (490. - 440.)
        B = 1.0
    elif w >= 490 and w < 510:
        R = 0.0
        G = 1.0
        B = -(w - 510.) / (510. - 490.)
    elif w >= 510 and w < 580:
        R = (w - 510.) / (580. - 510.)
        G = 1.0
        B = 0.0
    elif w >= 580 and w < 645:
        R = 1.0
        G = -(w - 645.) / (645. - 580.)
        B = 0.0
    elif w >= 645 and w <= 780:
        R = 1.0
        G = 0.0
        B = 0.0
    else:
        R = 0.0
        G = 0.0
        B = 0.0

    # intensity correction
    if w >= 380 and w < 420:
        SSS = 0.3 + 0.7*(w - 350) / (420 - 350)
    elif w >= 420 and w <= 700:
        SSS = 1.0
    elif w > 700 and w <= 780:
        SSS = 0.3 + 0.7*(780 - w) / (780 - 700)
    else:
        SSS = 0.0
    SSS *= 255

    return [int(SSS*R), int(SSS*G), int(SSS*B)]

The output value's range is 0 -- 255. The code could use some streamlining, but even in this form it is fast enough for an occasional image.

Here is whole visible spectrum as made by this function:

... and a line spectrum of our decades-old mercury vapour lamp:

Finally, in case you want to read more about computer colour science:
Rendering spectra
Colour Rendering of Spectra