Pretty much the same as https://gist.github.com/schoentoon/6176047 but this will run forever and run with inotify itself

gistfile1.txt

#!/usr/bin/python
from nbt import * # https://github.com/twoolie/NBT
import json

def generate():
  nbtfile = nbt.NBTFile("/path/to/scoreboard.dat", 'rb')
  deaths=dict()
  for tag in nbtfile["data"]["PlayerScores"]:
    if str(tag["Objective"]) == "Deaths": #Assuming the objective keeping track of the deaths is called "deaths"
      deaths[str(tag["Name"])] = int(str(tag["Score"]))
  
  deaths = sorted(deaths.items(), key=lambda x:x[1])
  deaths.reverse()
  
  with open('/output/deaths.json', 'w') as outfile:
    json.dump(deaths, outfile)

import pyinotify

wm = pyinotify.WatchManager()  # Watch Manager
mask = pyinotify.IN_CLOSE_WRITE  # watched events

class EventHandler(pyinotify.ProcessEvent):
  def process_IN_CLOSE_WRITE(self, event):
    if event.pathname.endswith("scoreboard.dat"):
      print "Regenerating"
      generate()

handler = EventHandler()
notifier = pyinotify.Notifier(wm, handler)
wdd = wm.add_watch('/path/to/world/data', mask, rec=True)

notifier.loop()