When working on a Flask project, you may want to override flask configurations
on different environments. Here are some suggestions.

A folder structure like the following might work well

/demo/
     __init__.py
     configs/
             __init__.py
             application.id
             default.py
             development.py
             production.py
             staging.py
             test.py
     controllers.py
     templates/
               index.html

In this structure, configs are plain python files and default is always loaded.
It is then merged with the environment-specific configuration (e.g. development).

It helps if the flask application is instantiated by a factory method/function.
Here are some ways to select the environment, each with higher precendence
than the previous one.

• read the contents of a file (in this example application.id)
• pass an environment variable (e.g. APP_ENV)

• Override with a variable (useful for testing)

  from os import path
  from flask import Flask, Blueprint
  from flask import current_app

  root = Blueprint("root", name)

  @root.route("/")
  def root_index():
  return "Hello from %s" % current_app.config.get("MYCONFIG")

  basepath = path.abspath(path.dirname(file))

  CONFIGS = "demo.configs"

  def config_object_for(override=None):

  if override:
      return ".".join([CONFIGS, override])
  
  from os import environ
  
  try:
      with open(path.join(basepath, 'configs/application.id')) as appid:
          env = appid.read().strip()
  except Exception, e:
      pass
  
  environment_variable = environ.get("APP_ENV")
  if environment_variable:
      env = environment_variable or "development"
  
  return ".".join([CONFIGS, env])
  

  def create_app(override=None):

  app = Flask(__name__)
  app.config.from_object(config_object_for('default'))
  app.config.from_object(config_object_for(override))
  app.register_blueprint(root)
  
  return app
  

  if name == 'main':
  create_app().run(debug=True)