environs 1.2.0

Install

pip install environs

Basic usage

# export GITHUB_USER=sloria
# export MAX_CONNECTIONS=100
# export SHIP_DATE='1984-06-25'
# export TTL=42
# export ENABLE_LOGIN=true
# export GITHUB_REPOS=webargs,konch,ped
# export COORDINATES=23.3,50.0

from environs import Env

env = Env()
# required variables
gh_user = env('GITHUB_USER')  # => 'sloria'
secret = env('SECRET')  # => raises error if not set

# casting
max_connections = env.int('MAX_CONNECTIONS')  # => 100
ship_date = env.date('SHIP_DATE')  # => datetime.date(1984, 6, 25)
ttl = env.timedelta('TTL')  # => datetime.timedelta(0, 42)

# providing a default value
enable_login = env.bool('ENABLE_LOGIN', False)  # => True
enable_feature_x = env.bool('ENABLE_FEATURE_X', False)  # => False

# parsing lists
gh_repos = env.list('GITHUB_REPOS')  # => ['webargs', 'konch', 'ped']
coords = env.list('COORDINATES', subcast=float)  # => [23.3, 50.0]

Supported types

The following are all type-casting methods of Env:

• env.str

• env.bool

• env.int

• env.float

• env.decimal

• env.list (accepts optional subcast keyword argument)

• env.dict (accepts optional subcast keyword argument)

• env.json

• env.datetime

• env.date

• env.timedelta (assumes value is an integer in seconds)

• env.url

• env.uuid

Handling prefixes

# export MYAPP_HOST=lolcathost
# export MYAPP_PORT=3000

with env.prefixed('MYAPP_'):
    host = env('HOST', 'localhost')  # => 'lolcathost'
    port = env.int('PORT', 5000)  # => 3000

Proxied variables

# export MAILGUN_LOGIN=sloria
# export SMTP_LOGIN={{MAILGUN_LOGIN}}

smtp_login = env('SMTP_LOGIN')  # =>'sloria'

Validation

# export TTL=-2
# export NODE_ENV='invalid'
# export EMAIL='^_^'


# simple validator
env.int('TTL', validate=lambda n: n > 0)
# => Environment variable "TTL" invalid: ['Invalid value.']

# using marshmallow validators
from marshmallow.validate import OneOf

env.str('NODE_ENV',
        validate=OneOf(['production', 'development'],
                        error='NODE_ENV must be one of: {choices}'))
# => Environment variable "NODE_ENV" invalid: ['NODE_ENV must be one of: production, development']

# multiple validators
from marshmallow.validate import Length, Email

env.str('EMAIL', validate=[Length(min=4), Email()])
# => Environment variable "EMAIL" invalid: ['Shorter than minimum length 4.', 'Not a valid email address.']

Serialization

# serialize to a dictionary of simple types (numbers and strings)
env.dump()
# {'COORDINATES': [23.3, 50.0],
# 'ENABLE_FEATURE_X': False,
# 'ENABLE_LOGIN': True,
# 'GITHUB_REPOS': ['webargs', 'konch', 'ped'],
# 'GITHUB_USER': 'sloria',
# 'MAX_CONNECTIONS': 100,
# 'MYAPP_HOST': 'lolcathost',
# 'MYAPP_PORT': 3000,
# 'SHIP_DATE': '1984-06-25',
# 'TTL': 42}

Defining custom parser behavior

# export DOMAIN='http://myapp.com'
# export COLOR=invalid

from furl import furl

# Register a new parser method for paths
@env.parser_for('furl')
def furl_parser(value):
    return furl(value)

domain = env.furl('DOMAIN')  # => furl('https://myapp.com')


# Custom parsers can take extra keyword arguments
@env.parser_for('enum')
def enum_parser(value, choices):
    if value not in choices:
        raise environs.EnvError('Invalid!')
    return value

color = env.enum('COLOR', choices=['black'])  # => raises EnvError

Note: Environment variables parsed with a custom parser function will be serialized by Env.dump without any modification. To define special serialization behavior, use Env.parser_from_field instead (see next section).

Marshmallow integration

# export STATIC_PATH='app/static'

# Custom parsers can be defined as marshmallow Fields
import pathlib

import marshmallow as ma

class PathField(ma.fields.Field):
    def _deserialize(self, value, *args, **kwargs):
        return pathlib.Path(value)

    def _serialize(self, value, *args, **kwargs):
        return str(value)

env.add_parser_from_field('path', PathField)

static_path = env.path('STATIC_PATH')  # => PosixPath('app/static')
env.dump()['STATIC_PATH']  # => 'app/static'

Reading .env files

# myapp/.env
DEBUG=true
PORT=4567

Call Env.read_env before parsing variables.

from environs import Env

env = Env()
# Read .env into os.environ
env.read_env()

env.bool('DEBUG')  # => True
env.int('PORT')   # => 4567

Why…?

License

MIT licensed. See the LICENSE file for more details.

1.2.0 (2017-01-12)

Features:

• Add url parser that returns a urllib.parse.ParseResult (#6). Thanks IlyaSemenov for the suggestion.

Bug fixes:

• Every instance of Env gets its own parser map, so calling env.parser_for for one instance doesn’t affect other instances.

1.1.0 (2016-05-01)

• Add Env.read_env method for reading .env files.

1.0.0 (2016-04-30)

• Support for proxied variables (#2).

• Backwards-incompatible: Remove env.get method. Use env() instead.

• Document how to read .env files (#1).

0.1.0 (2016-04-25)

• First PyPI release.