I've been using lightened rebound springs in Smith & Wesson revolvers over 25 years now, usually successfully, sometimes with humbling results.
Years ago, friends and I simply chopped one to three coils from rebound springs, did the requisite cursing as we coaxed springs and slides back into place, and hoped for the best. We usually ended up with lighter trigger pulls; unfortunately, we sometimes ended up with triggers that didn't return.
By and bye, I discovered Wolff, which offered sets of both rebound springs and main springs. Trial and error with various weights of springs let me slick up Smith & Wesson actions with far better results and no more calls to Brownells or Smith & Wesson for replacement springs. Along the way, I noticed some rebound slides were rough-surfaced, so I began to stone and polish them. Some frames were rough, I noticed, so I began to stone and polish those, too, and experiment with assorted lubricants.
I know a fellow who achieves nothing short of miraculous results by bending main springs in just a certain way, though he occasionally has to replace main springs that break. Instead of shortening or replacing rebound springs with lighter versions, he carefully removes small amounts of steel from the outer surfaces. I've seen him reduce double action pulls from 13 to 8 pounds.
Nothing takes the place of working on hammer and sear engagements, assuming you know what you're doing. That said™, most people don't know what they're doing, and probably shouldn't fool around unless they're ready, willing, and able to buy replacement parts and turn them over to competent pistolsmiths.
I've never owned or shot a Smith & Wesson revolver with a Python single action trigger, but can assure you it's possible to come very close with enough time, pistolsmithing trickery, and patience.