Source code for rororo.settings


Immutable Settings dictionary and various utilities to read settings values
from environment.

Module helps you to prepare and read settings inside your web application.


import calendar
import os
import time
import types

from distutils.util import strtobool
from importlib import import_module
from locale import LC_ALL, setlocale
from logging.config import dictConfig as setup_logging  # noqa: F401, N813
from typing import Any, Dict, Iterator, MutableMapping, Tuple, Union

Settings = Union[types.ModuleType, Dict[str, Any]]

[docs]def from_env(key: str, default: Any=None) -> Any: """Shortcut for safely reading environment variable. :param key: Environment var key. :param default: Return default value if environment var not found by given key. By default: ``None`` """ return os.environ.get(key, default)
[docs]def immutable_settings(defaults: Settings, **optionals: Any) -> types.MappingProxyType: r"""Initialize and return immutable Settings dictionary. Settings dictionary allows you to setup settings values from multiple sources and make sure that values cannot be changed, updated by anyone else after initialization. This helps keep things clear and not worry about hidden settings change somewhere around your web application. :param defaults: Read settings values from module or dict-like instance. :param \*\*optionals: Update base settings with optional values. In common additional values shouldn't be passed, if settings values already populated from local settings or environment. But in case of using application factories this makes sense:: from . import settings def create_app(**options): app = ... app.settings = immutable_settings(settings, **options) return app And yes each additional key overwrite default setting value. """ settings = {key: value for key, value in iter_settings(defaults)} for key, value in iter_settings(optionals): settings[key] = value return types.MappingProxyType(settings)
[docs]def inject_settings(mixed: Union[str, Settings], context: MutableMapping[str, Any], fail_silently: bool=False) -> None: """Inject settings values to given context. :param mixed: Settings can be a string (that it will be read from Python path), Python module or dict-like instance. :param context: Context to assign settings key values. It should support dict-like item assingment. :param fail_silently: When enabled and reading settings from Python path ignore errors if given Python path couldn't be loaded. """ if isinstance(mixed, str): try: mixed = import_module(mixed) except Exception: if fail_silently: return raise for key, value in iter_settings(mixed): context[key] = value
[docs]def is_setting_key(key: str) -> bool: """Check whether given key is valid setting key or not. Only public uppercase constants are valid settings keys, all other keys are invalid and shouldn't present in Settings dict. **Valid settings keys** :: DEBUG SECRET_KEY **Invalid settings keys** :: _PRIVATE_SECRET_KEY camelCasedSetting rel secret_key :param key: Key to check. """ return key.isupper() and key[0] != '_'
[docs]def iter_settings(mixed: Settings) -> Iterator[Tuple[str, Any]]: """Iterate over settings values from settings module or dict-like instance. :param mixed: Settings instance to iterate. """ if isinstance(mixed, types.ModuleType): for attr in dir(mixed): if not is_setting_key(attr): continue yield (attr, getattr(mixed, attr)) else: yield from filter(lambda item: is_setting_key(item[0]), mixed.items())
[docs]def setup_locale(locale: str, first_weekday: int=None) -> str: """Shortcut helper to setup locale for backend application. :param locale: Locale to use. :param first_weekday: Weekday for start week. 0 for Monday, 6 for Sunday. By default: None """ if first_weekday is not None: calendar.setfirstweekday(first_weekday) return setlocale(LC_ALL, locale)
[docs]def setup_timezone(timezone: str) -> None: """Shortcut helper to configure timezone for backend application. :param timezone: Timezone to use, e.g. "UTC", "Europe/Kiev". """ if timezone and hasattr(time, 'tzset'): tz_root = '/usr/share/zoneinfo' tz_filename = os.path.join(tz_root, *(timezone.split('/'))) if os.path.exists(tz_root) and not os.path.exists(tz_filename): raise ValueError('Incorrect timezone value: {0}'.format(timezone)) os.environ['TZ'] = timezone time.tzset()
[docs]def to_bool(value: Any) -> bool: """Convert string or other Python object to boolean. **Rationalle** Passing flags is one of the most common cases of using environment vars and as values are strings we need to have an easy way to convert them to boolean Python value. Without this function int or float string values can be converted as false positives, e.g. ``bool('0') => True``, but using this function ensure that digit flag be properly converted to boolean value. :param value: String or other value. """ return bool(strtobool(value) if isinstance(value, str) else value)