I think some of the later ones, like the Python Elite, were made in stainless. I don't think it was common on the early ones as the first widespread stainless revolver was the Smith's and Wesson's Model 60.
They are cool, but don't look as good as the deep buttery blue of Colt, or the super shiny nickel look. It used to be a good finish for a "working Python", but nowadays there are very few of those as the insane prices for them relegate most to occasional pampered range use or as safe queens. But, I'm sure there are still some out there rocking Pythons in their holsters, some cops even in certain areas.