Yet another wrapper object for environment variables. Does only the things I care about.

environment variables, environment-variables, python
pip install enviable==0.1.0



Author: Keryn Knight
Version: 0.1.0

A small module for wrapping over environment variables (pulled from os.environ) which provides convenience methods to fetch and check various data types (including iterables) in what I'd charitably hope is a sensible way.

Explicitly doesn't attempt to read from any .env or .envrc file, because that doesn't describe valid examples or which things may/should be set into the environment. It becomes an absolute pot-luck.

Tracks requested environment variables and their default/fallback/example values, and whether or not the fallback was used. Never tracks the actual environment value.

If this package isn't to your liking, there's plenty of others, and I'm largely suffering from Not-Invented-Here syndrome.

All methods exposed by the Environment accept a key and a default.

  • The key is the environment variable to search for.
  • The default MUST be a string, as it is subject to the same parsing as if it had been found in the environment, and thus serves as a documented example of a valid value to export as an environment variable. Enforced value documentation!

Example usage

A short series of some of the options:

from enviable import env, Environment
# the module level `env` is a premade `Environment` to work with and is
# roughly the same as `myenv = Environment(os.environ)`

DEBUG = env.bool("DEBUG", "off")
GIT_HASH = env.hex("COMMIT_REF", "11ff3fe8ccfa4bbd9c144f68b84c80f6")
SERVER_EMAIL = env.email("DEFAULT_EMAIL", "a@b.com")
DYANMIC_IMPORT = env.importable("MY_MODULE", "path.to.mymodule")
LOCAL_FILE = env.filepath("ACCESS_KEYS", "/valid/path/to/keys.json")
API_URL = env.web_address("API_URL", "https://example.com/")

# Iterables
NUMBERS = env.tuple("NUMBERS", "(12,3,456)", converter=env.ensure.int)
UNORDERED_NUMBERS = env.frozenset("NUMBERS", "12, 3, 456", converter=env.ensure.int)
DICTISH = env.dict("WOO", "a=1, b=2, c=3", key_converter=env.ensure.text, value_converter=env.ensure.int)

# Raw text *followed* by conversion
DEEPER_DEBUG = env.ensure.bool(env.text("DEBUG_DEEPLY", "1"))

Handling errors

Failing to successfully convert (or just validate) the value (whether from the environment or from the fallback) immediately halts execution by raising EnvironmentCastError which is a subclass of ValueError - it is recommended that you only catch the former.


Should be able to handle the following:

  • text
  • integer
  • boolean
  • uuid (with and without hyphens)
  • email (checks the string is email-like. Does not fully parse/validate, because that's a fool's errand)
  • hex (validates the string)
  • base64 encoded data (validates it decodes)
  • decimal
  • importable python paths (validates the string)
  • file paths (validates the file exists and is readable)
  • directories (validates the directory exists)
  • URLs (sanity-checks the string ... ish)
  • tuples/lists/sets/frozensets of any of the above
  • dictionaries, with separate key & value conversion
  • json

If Django is installed (sorry, I'm lazy) it should also handle:

  • datetime
  • date
  • time

Casting on iterables

Using any of env.tuple, env.list, env.set, env.frozenset, or env.dict allows each parsed value to be validated and optionally cast, with the caveat that the iterable is homogenous (that is, everything can be converted to an int or a uuid or whatever)

env.dict is slightly special in that it has arguments for key_converter and value_converter so that keys can have a different type to values. Both must still be homogenous.

Running the tests

Given a copy of the file enviable.py you ought to be able to do:

python enviable.py

and see the output of the various tests I've bothered with.


  • Examples of every type / method
  • More tests

The license

It's FreeBSD. There's should be a LICENSE file in the root of the repository, and in any archives.