envbool

Coerce environment variables to booleans.

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Every project ends up with some version of this:

DEBUG   = os.environ.get("DEBUG",   "").lower() in ("1", "true", "yes")
VERBOSE = os.environ.get("VERBOSE", "").lower() in ("1", "true", "yes")
CACHE   = os.environ.get("CACHE",   "").lower() in ("1", "true", "yes")

envbool replaces that:

from envbool import envbool

DEBUG   = envbool("DEBUG")
VERBOSE = envbool("VERBOSE")
CACHE   = envbool("CACHE")

It also handles strict mode, warnings, custom value sets, config files, and a CLI for shell scripts.

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Installation

pip install envbool
# or
uv add envbool

Usage

Lenient by default. Anything not recognized as truthy returns False. Unset and empty variables return the default.

from envbool import envbool

DEBUG = envbool("DEBUG")                    # False if unset or empty
CACHE = envbool("CACHE", default=True)      # True if unset or empty

The built-in truthy values are true, 1, yes, on. Comparison is case-insensitive.

Strict mode raises InvalidBoolValueError for unrecognized values — useful for catching typos in production config.

from envbool import envbool, InvalidBoolValueError

try:
    USE_SSL = envbool("USE_SSL", strict=True)
except InvalidBoolValueError as e:
    print(f"Bad value for USE_SSL: {e.value!r}")
    sys.exit(1)

Extend the value sets when your environment uses non-standard strings.

FEATURE = envbool("FEATURE_FLAG", extend_truthy={"enabled", "y"})

Coerce an arbitrary string (not from os.environ) with to_bool:

from envbool import to_bool

to_bool("yes")                  # True
to_bool("0")                    # False
to_bool("maybe", strict=True)   # raises InvalidBoolValueError

CLI

The envbool command exits 0 for truthy and 1 for falsy, so it works naturally in shell scripts.

# Control flow via exit code
envbool DEBUG && echo "debug is on"

# Print the resolved value
echo "Verbose: $(envbool --print VERBOSE)"

# Pipe a string
echo "yes" | envbool && echo "truthy"

# Strict mode
envbool --strict ENABLE_CACHE || echo "cache is off or misconfigured"

Configuration

Put shared defaults in envbool.toml (or [tool.envbool] in pyproject.toml) at your project root:

strict = true
extend_truthy = ["enabled"]
extend_falsy  = ["disabled"]

envbool walks up from the current directory to find the nearest config file, then falls back to a user-level config (~/.config/envbool/config.toml on Linux/macOS). Function arguments always override the config.

Set ENVBOOL_NO_CONFIG=1 to skip config discovery entirely.

API

Symbol	Description
envbool(var, ...)	Read an env var and return bool
to_bool(value, ...)	Coerce a string to bool
load_config()	Inspect the loaded config
DEFAULT_TRUTHY	frozenset of built-in truthy strings
DEFAULT_FALSY	frozenset of built-in falsy strings
InvalidBoolValueError	Raised in strict mode on unrecognized values
ConfigError	Raised when a config file is malformed

Both envbool() and to_bool() accept the same keyword arguments: default, strict, warn, truthy, falsy, extend_truthy, extend_falsy. truthy/falsy replace the effective set; extend_truthy/extend_falsy add to it.