Empty chamber was for single action revolver with hammer mounted firing pin rest on the primer. Python has frame mounted firing pin and firing pin don't rest on the primer, no need to leave one empty chamber.
The double action revolver as made by Colt has been as safe a machine as is humanly possible to build since the early 1900's.
S&W's have been totally safe since WWII, Ruger's and Dan Wesson's always were.
Essentially it's impossible to get one to fire accidentally UNLESS the trigger is pulled.
No amount of dropping or beating on it can cause it fire under any circumstances short of throwing it loaded into a fire.
As above the empty chamber was a necessary step in the old single action pistols that could fire if the hammer was struck.
In short, there's no good reason to leave an empty chamber in a modern double action revolver.
The old gag "We were fighting and the gun just went off" is bogus...... someone pulled the trigger.