When you get into blood python sub adults and larger it changes to Pounds. I'm sure other large thick snakes also get measured in pounds.
The 38 Lb Female I sold would have been 17236 grams. Granted since I don't have a gram scale that goes that high and I had to use the bathroom scale with me holding her any conversion to grams would have been a rough estimate that could have been off by 500 grams or so.