typedenv.py 1.0.1

Load environment variables with class type hints

typedenv.py

Load environment variables with class type hints

🚀 Quickstart

The library supports type hints for str, int, float, and bool out of the box.

import typedenv

# Assuming the given environment variables
# $ export LOG_LEVEL=INFO
# $ export POOL_SIZE=100
# $ export DEBUG=1
# $ export SCALING=1.5

class EnvConfig(typedenv.EnvLoader):
    LOG_LEVEL: str
    POOL_SIZE: int
    DEBUG: bool
    SCALING: float

env = EnvConfig()
assert env.LOG_LEVEL == "INFO"
assert env.POOL_SIZE == 100
assert env.DEBUG == True
assert env.SCALING == 1.5

📚 Documentation

Environment variables will be loaded into the instance of your class on initialization. The name of the class attributes will be used to look up the corresponding environment variables. Only attributes that are capitalized and are type-hinted will be loaded.

Optional Keys

By default, a ValueError is raised if an environment key matching your class attribute is not found. To make keys optional, you can either give them default values, use typing.Optional, or union your type with None.

class EnvConfig(typedenv.EnvLoader):
    DEBUG: bool = True
    API_KEY: str | None
    MAX_SIZE: typing.Optional[int]

Supporting Additional Types

Additional support for types can be added by providing a converting function through typedenv.Converter. These can either passed in as a class option or through typing.Annotated for a specific key.

def str_list(value: str) -> list[str]:
    return value.split(",")

def to_path(value: str) -> Path:
    return Path(value)

class EnvConfig(typedenv.EnvLoader, converters=[typedenv.Converter(str_list)]):
    CLUSTERS: list[str]
    CONFIG_FILE: typing.Annotated[Path, typedenv.Converter(to_path)]

Validation and Transformation

In addition to supporting new types, typedenv.Converter can also be used to validate and transform already supported types.

def validate_str(value: str) -> str:
    if not value.isalnum():
        raise ValueError("only letters/numbers allowed")
    return value.upper()

class EnvConfig(typedenv.EnvLoader, converters=[typedenv.Converter(validate_str)]):
    API_KEY: str

Mutability

By default, attributes loaded with an environment variable will be immutable. This can be disabled through the frozen option.

class EnvConfig(typedenv.EnvLoader, frozen=False):
    TIMEOUT: int

config = EnvConfig()
config.TIMEOUT = 30

One-time Loading

By default, environment variables will be loaded into the class every time a new instance is created. You can use the singleton option to convert your class into a Singleton and ensure it will only load from environment variables on the first initialization.

class EnvConfig(typedenv.EnvLoader, singleton=True):
    LOG_LEVEL: str

assert EnvConfig() is EnvConfig()

Subclass Overriding

Your EnvLoader class can be further subclassed, which can be useful for type narrowing keys required by certain modules in your application, or for adding default values.

class EnvConfig(typedenv.EnvLoader):
    LOG_LEVEL: str
    GOOGLE_API_KEY: str | None

class GoogleRequiredConfig(EnvConfig):
    GOOGLE_API_KEY: str

class TestConfig(EnvConfig):
    GOOGLE_API_KEY = "fake-google-key"