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Typed environment variable parsing for Python

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Version 0.1.6

Typed environment variable parsing for Python

Table of Contents generated with mdformat-toc


Typenv does environment variable parsing with an API almost identical to the excellent environs. There are a few reasons why typenv might be preferred:

  • Type annotated typecast functions: type checkers are able to understand types of parsed environment variables.
  • More flexible prefix manipulation of environment variable names.
  • Validation of environment variable names.
  • Optional automatic uppercasing of environment variable names.
  • Ability to generate a .env.example that shows expected types of environment variables.
  • Less dependencies. No marshmallow required.


Installing from PyPI repository (

pip install typenv



Set environment variables:

export NAME='Harry Potter'
export AGE=14
export IS_WIZARD=true
export BANK_BALANCE=134599.01
export LUCKY_NUMBERS=7,3,11
export EXTRA_DETAILS='{"friends": ["Hermione", "Ron"]}'

Parse the values in Python:

from typenv import Env

env = Env()

NAME = env.str("NAME")  # => "Harry Potter"
AGE ="AGE")  # => 14
IS_WIZARD = env.bool("IS_WIZARD")  # => True
BANK_BALANCE = env.decimal("BANK_BALANCE")  # => decimal.Decimal("134599.01")
LUCKY_NUMBERS = env.list("LUCKY_NUMBERS", subcast=int)  # => [7, 3, 11]
EXTRA_DETAILS = env.json("EXTRA_DETAILS")  # => {"friends": ["Hermione", "Ron"]}

# Optional settings must have a default value
IS_DEATH_EATER = env.bool("IS_DEATH_EATER", default=False)  # => False

Supported types

The types supported by typenv are:

  • env.str
  • env.bool
  • env.float
  • env.decimal
  • env.json
  • env.list
    • Takes a subcast argument for casting list items to one of str, int , bool, float or decimal.Decimal
  • env.bytes

Default values

Normally, if an environment variable is not found, typenv raises an exception. If a default value is provided, however, that will be returned instead of raising.

from typenv import Env

env = Env()

BOOL = env.bool("NON_EXISTING_NAME", default=False)  # => False
LIST = env.list("NON_EXISTING_NAME", default=["a", "b"])  # => ["a", "b"]
OPTIONAL_INT ="NON_EXISTING_NAME", default=None)  # => None

Name prefixes

TODO: document here

Name character set

Typenv validates environment variable names. By default, the set of allowed characters includes upper case ASCII letters, digits and the underscore (_).

The set of allowed characters can be configured:

from typenv import Env


Name uppercasing

export UPPER_CASE_NAME=true
from typenv import Env

# Environment variable names in type cast methods will automatically be upper
# cased when `upper=True` is set here.
env = Env(upper=True)

NAME = env.bool("upper_casE_Name")


export NAME='Harry Potter'
export AGE=14
from typenv import Env

env = Env()

# A single validator function
NAME = env.str("NAME", validate=lambda n: n.startswith("Harry"))

# A validator function can signal error by raising an exception
def is_positive(num):
    if num <= 0:
        raise Exception("Number is not positive")

# A validator function can alternatively return `False` to signal an error
def is_less_than_thousand(num):
    if num >= 1000:
        return False
    return True

# Multiple validator functions can be passed as an iterable of callables
AGE ="AGE", validate=(is_positive, is_less_than_thousand))

Reading from a .env file

TODO: document here

Dumping parsed values

export SOME_STR=blaablaa
export SOME_INT=99
from typenv import Env, ParsedValue

env = Env()

SOME_STR = env.str("SOME_STR")

assert env.dump() == {
    "SOME_INT": ParsedValue(value=99, type="int", optional=False),
    "SOME_STR": ParsedValue(value="blaablaa", type="str", optional=False),


The public API of this library is almost an exact copy of environs, which is based on envparse and django-environ. Credit for the interface goes to the authors of those libraries.

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