Python Use Config Files

Description

One of the easiest ways you can differentiate between environments with python apps is to create yml files in the application’s directory and set an environmental variable as the environment. I haven’t gotten around to re-writing all my applications (Function Apps), but I plan to do this soon.

To Resolve:

1. Create your regular .env file as follows like:

   STAGE=production
   

   • If using a Function App, just set the environmental variable in the Application Settings blade and then do like usual

   def import_creds():
      '''
      Gets secrets from Azure Keyvault as an application
      Secret values are stored in the Function App under Configuration
         
      Example of how to call from main():
      keyvault_creds = import_creds()
      logging.info(f"client_id: { keyvault_creds['client_id'] }")
      logging.info(f"client_secret: { keyvault_creds['client_secret'] }")
      logging.info(f"tenant: { keyvault_creds['tenant'] }")
      logging.info(f"vault_name: { keyvault_creds['vault_name'] }")
      '''
   
      try:
         creds = {}
         creds["client_id"] = os.environ["client_id"]
         creds["client_secret"] = os.environ["client_secret"]
         creds["tenant"] = os.environ["tenant"]
         creds["vault_name"] = os.environ["vault_name"]
      except KeyError:
         logging.error("Unable to get env vars")
      except Exception as e:
         logging.error(f"Generic Catch: {str(e)}")
   
      return creds
   

2. But this time, set a config file in the directory called .dev.config.yaml with the contents of:

   servers:
      - host-a.domain.com
      - host-b.domain.com
      - networks:
         - 10.20.20.0
         - 10.30.30.30
   
   endpoints:
      - service_now: https://myendpoint-dev.com
      - key: dev-adcd1234567890
   

   • Also create a .prod.config.yaml in the same directory with the values of:

   servers:
      - host-c.domain.com
      - host-d.domain.com
      - networks:
         - 10.20.20.0
         - 10.30.30.30
   
   endpoints:
      - service_now: https://myendpoint-prod.com
      - key: prod-adcd1234567890
   

   • Then, either in its own file like config.py or inside your helpers.py, import them:

   import os
   import sys
   from pathlib import Path
   import yaml
   
   from dotenv import load_dotenv
   
   load_dotenv()
   
   try:
      APP_ENV = os.getenv('STAGE', 'development')
   except Exception as e:
      print(f"Unable to get environmental variable: {STAGE}")
      exit(1)
   
   CONFIG_FILES = {
      'development': '.dev.config.yaml',
      'production': '.prod.config.yaml',
   }
   
   try:
      conf_file = Path(__file__).parent.joinpath(CONFIG_FILES[APP_ENV])
   except KeyError:
      print(f"Environment config file not found. Provided: '{APP_ENV}'. Accepted: {CONFIG_FILES}")
      sys.exit(1)
   
   with open(conf_file, 'r') as f:
      CONFIG = yaml.safe_load(f)
   

3. Make sure your requirements.txt includes the following

   PyYAML==5.3.1
   python-dotenv==0.14.0
   

4. Now, in your main code, just call the same config regardless of the environment. For example, in a main.py:

   from config import CONFIG
   
   servers = CONFIG['servers']
   print(servers)
   # ['host-c.domain.com', 'host-d.domain.com', {'networks': ['10.20.20.0', '10.30.30.30']}]
   print(servers[0])
   # host-c.domain.com
   print(servers[1])
   # host-d.domain.com
   print(servers[2]['networks'])
   # ['10.20.20.0', '10.30.30.30']
   print(servers[2]['networks'][0])
   # 10.20.20.0
   
   endpoints = CONFIG['endpoints']
   print(endpoints)
   # [{'service_now': 'https://myendpoint-dev.com'}, {'key': 'dev-adcd1234567890'}]
   
   sn = CONFIG['endpoints'][0]['service_now']
   print(sn)
   # https://myendpoint-dev.com
   
   key = CONFIG['endpoints'][1]['key']
   print(key)
   # dev-adcd1234567890