old_contents: from flask import Flask
  
  from . import views
  
  
  app = Flask(__name__, instance_relative_config=True)
  
  # Load the default configuration
  app.config.from_object('config.default')
  
  # Load the configuration from the instance folder
  app.config.from_pyfile('config.py')
  
  # Load the file specified by the APP_CONFIG_FILE environment variable
  # Variables defined here will override those in the default configuration
  app.config.from_envvar('APP_CONFIG_FILE')   
  
  app.register_blueprint(views.blueprint)
  
new_contents: from flask import Flask
  
  from . import views
  
  
  app = Flask(__name__, instance_relative_config=True)
  
  # Load the default configuration
  app.config.from_object('config.default')
  
  # Tru to load the configuration from the instance folder
  try:
      app.config.from_pyfile('config.py')
  except FileNotFoundError:
      pass
  
  # Load the file specified by the APP_CONFIG_FILE environment variable
  # Variables defined here will override those in the default configuration
  app.config.from_envvar('APP_CONFIG_FILE')   
  
  app.register_blueprint(views.blueprint)
  
subject: Make instance folder optional