Flask application configuration using an environment variable and YAML

app.py

os
from flask_extended import Flask

app = Flask(__name__)
app.config.from_yaml(os.join(app.root_path, 'config.yml'))

config.yml

COMMON: &common
  SECRET_KEY: insecure
    
DEVELOPMENT: &development
  <<: *common
  DEBUG: True
  
STAGING: &staging
  <<: *common
  SECRET_KEY: sortasecure
  
PRODUCTION: &production
  <<: *common
  SECRET_KEY: shouldbereallysecureatsomepoint
    
    
  

flask_extended.py

import os
import yaml

from flask import Flask as BaseFlask, Config as BaseConfig

class Config(BaseConfig):
    """Flask config enhanced with a `from_yaml` method."""
    
    def from_yaml(self, config_file):
        env = os.environ.get('FLASK_ENV', 'development')
        self['ENVIRONMENT'] = env.lower()
        
        with open(config_file) as f:
            c = yaml.load(f)
            
        c = c.get(env, c)
            
        for key in c.iterkeys():
            if key.isupper():
                self[key] = c[key]
                
class Flask(BaseFlask):
    """Extended version of `Flask` that implements custom config class"""
    
    def make_config(self, instance_relative=False):
        root_path = self.root_path
        if instance_relative:
            root_path = self.instance_path
        return Config(root_path, self.default_config)