generate .shuttle.json for list of amazon ec2 instances

#!/usr/bin/env python

# @author: eugene.santos13@gmail.com
# this will generate json structure for .shuttle.json

import json
import sys, getopt

def parse_opt(argv):
   cert_path = ''
   environment = ''
   name = ''
   username = ''
   try:
      opts, args = getopt.getopt(argv,"e:c:n:u:",["env=","cert=","name=","username="])
   except getopt.GetoptError:
      print "%s --env production --cert ~/cert.pem --name \"accessname\" --username ec2-user" % sys.argv[0]
      sys.exit(2)
   for opt, arg in opts:
      if opt == '-h':
         print "%s --env production --cert ~/cert.pem --name \"accessname\" --username ec2-user" % sys.argv[0]
         sys.exit()
      elif opt in ("-e", "--env"):
         environment = arg
      elif opt in ("-c", "--cert"):
         cert_path = arg
      elif opt in ("-n", "--name"):
         name = arg
      elif opt in ("-u", "--username"):
         username = arg                  

   return { "cert_path": cert_path, "environment" : environment, "name": name, "username": username }


opts = {}

if __name__ == '__main__':
    opts = parse_opt(sys.argv[1:])

    fo = open("file.txt", "r+")
    serv = []

    for i, ip in enumerate(fo.readlines()):
        
        ip = ip.rstrip('\n')
        serv.append(
            { 
                "%s %s" % (opts["name"], ip): [ 
                    { 
                        "cmd": "ssh %s@%s -i %s" % (opts["username"], ip, opts['cert_path']), 
                        "name": "%s %s" % (opts["name"], i)
                    } 
                ]
            })

    print json.dumps(serv,indent=2, separators=(',', ': '))

    fo.close()