roskarl 3.1.28

Environment variable helpers

Roskarl

Is a tiny module for environment variables

Requires

Python 3.11.0+

How to install

uv pip install roskarl

Example usage

from roskarl import (
    env_var,
    env_var_bool,
    env_var_cron,
    env_var_custom,
    env_var_duration,
    env_var_enum,
    env_var_interval_expression,
    env_var_interval_expression_extended,
    env_var_float,
    env_var_int,
    env_var_iso8601_datetime,
    env_var_list,
    env_var_log_level,
    env_var_path,
    env_var_rfc3339_datetime,
    env_var_secret,
    env_var_tz,
    env_var_url,
    env_var_dsn,
    DSN,
    Secret,
)

All functions return None if the variable is not set. An optional default parameter can be provided to return a fallback value instead.

Pass required=True to raise instead of returning None — type checkers will narrow the return type accordingly (e.g. str instead of str | None), so no assert is needed at callsites.

str (returns str)

value = env_var(name="STR_VAR", default="fallback")

bool (returns bool — accepts true or false (case insensitive))

value = env_var_bool(name="BOOL_VAR")

tz (returns str if value is a valid IANA timezone (e.g. Europe/Stockholm))

value = env_var_tz(name="TZ_VAR")

list (returns list[str] if value is splittable by separator)

value = env_var_list(name="LIST_VAR", separator="|")

int (returns int if value is numeric)

value = env_var_int(name="INT_VAR")

float (returns float if value is a float)

value = env_var_float(name="FLOAT_VAR")

cron (returns str if value is a valid cron expression)

value = env_var_cron(name="CRON_VAR")

interval expression (returns str if value is a valid offset-free 5-field cron expression)

value = env_var_interval_expression(name="INTERVAL_VAR")

interval expression extended (returns str if value is a valid offset-free 6-field cron expression)

value = env_var_interval_expression_extended(name="INTERVAL_EXTENDED_VAR")

datetime (ISO8601) (returns datetime if value is a valid ISO8601 datetime string — timezone is optional)

value = env_var_iso8601_datetime(name="DATETIME_VAR")

datetime (RFC3339) (returns datetime if value is a valid RFC3339 datetime string — timezone is required)

value = env_var_rfc3339_datetime(name="DATETIME_VAR")

url (returns str if value has a scheme + netloc, e.g. https://example.com)

value = env_var_url(name="API_URL")

secret (returns Secret — wraps the value so it can't accidentally be logged)

repr() and str() return ***. Call .reveal() at the point of use.

key = env_var_secret(name="API_KEY", required=True)
print(key)            # ***
stripe.api_key = key.reveal()

path (returns pathlib.Path)

Pass must_exist=True to fail fast if the path is not present on disk

value = env_var_path(name="CONFIG_PATH", must_exist=True)

enum (returns an instance of your Enum subclass)

Matches against each member's .value. Raises ValueError if no match.

from enum import Enum
class Mode(Enum):
    LIVE = "live"
    DRY_RUN = "dry-run"

value = env_var_enum(name="MODE", enum_class=Mode, required=True)

duration (returns timedelta)

Parses compound duration strings using suffixes ms, s, m, h, d. Spaces between parts are tolerated.

value = env_var_duration(name="REQUEST_TIMEOUT", default=timedelta(seconds=30))
# accepts: "30s", "5m", "1h30m", "500ms", "7d", "1h 30m"

log level (returns int matching Python's logging levels)

Accepts DEBUG, INFO, WARNING/WARN, ERROR, CRITICAL/FATAL (case-insensitive).

import logging
level = env_var_log_level(name="LOG_LEVEL", default=logging.INFO)
logging.basicConfig(level=level)

custom (returns whatever your parser returns)

Escape hatch for types without a dedicated helper — pass any Callable[[str], T].

from uuid import UUID
value = env_var_custom(name="UUID_VAR", parser=UUID, required=True)  # type: UUID

DSN

Note: Special characters in passwords must be URL-encoded.

from urllib.parse import quote
password = 'My$ecret!Pass@2024'
encoded = quote(password, safe='')
print(encoded)  # My%24ecret%21Pass%402024 <--- use this

value = env_var_dsn(name="DSN_VAR")

returns DSN object if value is a valid DSN string, formatted as:

postgresql://username:password@hostname:5432/database_name

The DSN object exposes the following attributes:

Attribute	Type	Example
scheme	str	postgresql
host	str	hostname
port	int	5432
username	str	username
password	str	password
database	str	database_name

---

Testing

Tests use pytest. Run the full suite:

pytest tests/

Release

See RELEASE.md for instructions on how to publish a new version.