$ sudo pip install Flask-Environments

# config.py
import os

class Config(object):
  DEBUG = True
  BASEDIR = os.path.abspath(os.path.dirname(__file__))

  HOST = '0.0.0.0'
  PORT = '8000'

class Development(Config):  # inherit from Config
  pass

class Production(Config):
  DEBUG = False
  HOST = '127.0.0.1
  PORT = 14000

from flask import Flask
from flask_environments import Environments

app = Flask(__name__)
env = Environments(app)
env.from_object('config')

$ FLASK_ENV=PRODUCTION gunicorn -b 127.0.0.1:14000 myapp:app