JSONAppend.py

import json

#This is going to fetch our lines one-by-one
#Useful for super-huge files
class JSONFetcher():
	def __init__(self, fileName):
		self.fileName = fileName + '.json'

	def fetch(self):
		print("fetching...")

		with open(self.fileName, 'rb') as f:
			for line in f:
				yield json.loads(line)
				
				
if __name__ == "__main__":
  filename = "MY_FILENAME"
  
  sourcefile = JSONFetcher(filename)
  outfile = open("OUTFILE", 'wb')
  
  for record in sourcefile.fetch():
    record['ADDED_KEY'] = "NEW_VALUE_HERE"]
    
    jsonOut = json.dumps(record)
    outfile.write(jsonOut + '\n')
    
  
  outfile.close()