xsettings 1.4.0

Ways to document, centeralize, retreive and validate settings.

• Introduction
• Documentation
• Install
• Quick Start
• Licensing

Introduction

Helps document and centralizing settings in a python project/library.

Facilitates looking up BaseSettings from retrievers, such as an environmental variable retriever.

Converts and standardizes any retrieved values to the type-hint on the setting attribute (such as bool, int, datetime, etc).

Interface to provide own custom retrievers, to grab settings/configuration from wherever you want.

Retrievers can be stacked, so multiple ones can be consulted when retrieving a setting.

See xsettings docs.

Documentation

📄 Detailed Documentation | 🐍 PyPi

Install

# via pip
pip install xsettings

# via poetry
poetry add xsettings

Quick Start

from xsettings import EnvVarSettings, SettingsField
from xsettings.errors import SettingsValueError
from typing import Optional
import dataclasses
import os

# Used to showcase looking up env-vars automatically:
os.environ['app_version'] = '1.2.3'

# Used to showcase complex setting types:
@dataclasses.dataclass
class DBConfig:
    @classmethod
    def from_dict(cls, values: dict):
        return DBConfig(**values)

    user: str
    host: str
    password: str


# Some defined settings:
class MySettings(EnvVarSettings):
    app_env: str = 'dev'
    app_version: str
    api_endpoint_url: str
    
    some_number: int

    # For Full Customization, allocate SettingsField,
    # In this case an alternate setting lookup-name
    # if you want the attribute name to differ from lookup name:
    token: Optional[str] = SettingsField(name='API_TOKEN')

    # Or if you wanted a custom-converter for a more complex obj:
    db_config: DBConfig = SettingsField(
        converter=DBConfig.from_dict
    )

# BaseSettings subclasses are singleton-like dependencies that are
# also injectables and lazily-created on first-use.
# YOu can use a special `BaseSettings.grab()` class-method to
# get the current settings object.
#
# So you can grab the current MySettings object lazily via
# its `grab` class method:
MySettings.grab().some_number = 3

assert MySettings.grab().some_number == 3

# You can also use a proxy-object, it will lookup and use
# the current settings object each time its used:
my_settings = MySettings.proxy()

# Here I showcase setting a dict here and using the converter
# I defined on the SettingsField to convert it for me:
my_settings.db_config = {
    'user': 'my-user',
    'password': 'my-password',
    'host': 'my-host'
}


expected = DBConfig(
    user='my-user',
    password='my-password',
    host='my-host'
)

# The dict gets converted automatically to the DBConfig obj:
assert MySettings.grab().db_config == expected

# If you set a setting with the same/exact type as
# it's type-hint, then it won't call the converter:
my_settings.db_config = expected

# It's the same exact object-instance still (ie: not changed/converted):
assert my_settings.db_config is expected


# Will use the default value of `dev` (default value on class)
# since it was not set to anything else and there is no env-var for it:
assert my_settings.app_env == 'dev'

# EnvVarSettings (superclass) is configured to use the EnvVar retriever,
# and so it will find this in the environmental vars since it was not
# explicitly set to anything on settings object:
assert my_settings.app_version == '1.2.3'

# Any BaseSettings subclass can use dependency-injection:
assert my_settings.token is None

with MySettings(token='my-token'):
    assert my_settings.token == 'my-token'

    # Parent is still consulted for any settings unset on child but set on parent:
    assert my_settings.db_config == expected

    # Can set settings like you expect,
    # this will go into the child created in above `with` statement:
    my_settings.app_env = 'prod'

    assert my_settings.app_env == 'prod'

# After `with` child is not the current settings object anymore,
# reverts back to what it was before:
assert my_settings.token is None

try:
    # If a setting is undefined and required (ie: not-optional),
    # and it was not set to anything nor is there a default or an env-var for it;
    # BaseSettings will raise an exception when getting it:
    print(my_settings.api_endpoint_url)
except SettingsValueError as e:
    assert True
else:
    assert False

try:
    # `SettingsValueError` inherits from both AttributeError and ValueError,
    # as the error could be due to either aspect; so you can also do an except
    # for either standard error:
    print(my_settings.api_endpoint_url)
except ValueError as e:
    assert True
else:
    assert False

Licensing

This library is licensed under the MIT-0 License. See the LICENSE file.