envparse 0.1.6

Simple Environment Variable Parsing

If you use Heroku and/or subscribe to the tenets of the 12 Factor App you’ll be using a lot of environment variable-based configuration in your app. os.environ is a great choice to start off with but over time you’ll find yourself duplicating quite a bit of code around handling raw environment variables.

envparse aims to eliminate this duplicated, often inconsistent parsing code and instead provide a single, easy-to-use wrapper that handles:

• Casting environment variables to a type:

  MAIL_ENABLED=1
  
  mail_enabled = env('MAIL_ENABLED', cast=bool)
  if mail_enabled:
      send_mail(...)

• Specifying defaults:

  max_rows = env('MAX_ROWS', cast=int, default=100)
  rows = query(limit=max_rows)

• Proxying values, useful in Heroku for wiring up the environment variables they provide to the ones that your app actually uses:

  MAILGUN_SMTP_LOGIN=foo          # Heroku provides this with add-on
  SMTP_LOGIN={MAILGUN_SMTP_LOGIN} # App uses proxied variable
  
  smtp_login = env('SMTP_LOGIN')
  assert smtp_login == 'foo'

Now if you switch to using Mandrill as an email provider, instead of having to modify your app, you can simply make a configuration change:

SMTP_LOGIN={MANDRILL_UESRNAME}

• Define a schema so you can only need to provide the type and defaults once:

  MAIL_ENABLED=0
  SMTP_LOGIN=bar
  
  # Bind schema to Env object to get schema-based lookups
  env = Env(MAIL_ENABLED=bool, SMTP_LOGIN=(str, 'foo'))
  assert env('MAIL_ENABLED') is False
  assert env('SMTP_LOGIN') == 'bar'
  
  ...later in the code...
  
  if env('MAIL_ENABLED'):
      send_email(...)