SunsetSettings 0.5.5

SunsetSettings: a type-safe, extensible settings system with inheritance.

SunsetSettings

SunsetSettings is a library that provides facilities to declare and use settings for an interactive application in a type-safe manner, and load and save them in a simple INI-like format.

The settings can safely store arbitrary types, and can be structured in an arbitrarily deep hierarchy of subsections, which allows you to implement overrides per project, per folder, per user, etc.

It is mainly intended for software where the user can change settings on the fly, for instance with a settings dialog, and those settings need to be preserved between sessions.

Examples

Creating settings:

>>> from sunset import Bunch, Key, List, Settings

>>> class BackupToolSettings(Settings):
...
...     class UI(Bunch):
...
...         class Font(Bunch):
...             name = Key(default="Arial")
...             size = Key(default=12)
...
...         font  = Font()
...         theme = Key(default="") 
...
...     class Backup(Bunch):
...         folder      = Key(default="~")
...         destination = Key(default="/mnt/backups")
...         compress    = Key(default=True)
...
...     ui = UI()
...     backups = List(Backup())

Loading and saving settings:

>>> from sunset import AutoSaver

>>> def main_program_loop(settings: BackupToolSettings):
...     ...

>>> settings = BackupToolSettings()
>>> with AutoSaver(settings, "~/.config/backup.conf"):  # doctest: +SKIP
...    main_program_loop(settings)

Using settings values:

>>> def do_backup(source: str, destination: str, use_compression: bool):
...     ...

>>> def do_all_backups(settings: BackupToolSettings):
...     for backup in settings.backups:
...         do_backup(
...             source=backup.folder.get(),
...             destination=backup.destination.get(),
...             use_compression=backup.compress.get(),
...         )

>>> do_all_backups(settings)

Changing settings values:

>>> def update_font_settings(
...     font_name: str,
...     font_size: int,
...     font_settings: BackupToolSettings.UI.Font,
... ):
...     font_settings.name.set(font_name)
...     font_settings.size.set(font_size)

>>> update_font_settings("Verdana", 11, settings.ui.font)

Reacting to setting value changes:

>>> def apply_theme(new_theme_name: str):
...     ...

>>> def setup_theme_change_logic(ui_settings: BackupToolSettings.UI):
...     ui_settings.theme.onValueChangeCall(apply_theme)

>>> setup_theme_change_logic(settings.ui)

Features

Type safety

SunsetSettings is type-safe; that is to say, if you are holding it wrong, type checkers will tell you.

>>> from sunset import Key

>>> # Types can be inferred from the provided default value:
>>> number_of_ponies = Key(default=0)
>>> number_of_ponies
<Key[int]:(0)>
>>> number_of_ponies.set(6)  # Works!
True
>>> number_of_ponies.set("six")  # Type error!
False
>>> number_of_ponies.get()  # Value is unchanged.
6
>>> from typing import TYPE_CHECKING
>>> if TYPE_CHECKING:
...     reveal_type(number_of_ponies.get())
>>> # Revealed type is "builtins.int"

Extensibility

You can store arbitrary types in your SunsetSettings provided that you also provide a serializer for that type. (See the API reference.)

>>> import re
>>> from typing import Optional, TYPE_CHECKING

>>> class Coordinates:
...     def __init__(self, x: int, y: int) -> None:
...         self.x = x
...         self.y = y

>>> class CoordinatesSerializer:
...     def toStr(self, coord: Coordinates) -> str:
...         return f"{coord.x},{coord.y}"
...
...     def fromStr(self, string: str) -> Optional[Coordinates]:
...         x, y = string.split(",", 1)
...         if not x.isdigit() or not y.isdigit():
...             return None
...         return Coordinates(int(x), int(y))

>>> from sunset import Key
>>> coordinates = Key(
...     default=Coordinates(0, 0), serializer=CoordinatesSerializer()
... )
>>> if TYPE_CHECKING:
...     reveal_type(coordinates.get())
>>> # Revealed type is "Coordinates"
>>> print(repr(coordinates))
<Key[Coordinates]:(0,0)>

Inheritance

SunsetSettings lets the user have a general set of settings that can be partially overriden in subsections used in specific cases (much like your VSCode settings can be overriden by workspace, for instance). The hierarchy of subsections can be arbitrarily deep.

>>> from sunset import Key, Settings

>>> class Animals(Settings):
...     limbs: Key[int] = Key(default=4)
... 
>>> animals = Animals()
>>> octopuses = animals.newSection(name="octopuses")
>>> octopuses.limbs.get()
4
>>> octopuses.limbs.set(8)
True
>>> octopuses.limbs.get()
8
>>> animals.limbs.get()
4
>>> octopuses.limbs.clear()
>>> octopuses.limbs.get()
4

Callbacks

Each setting key can be given callbacks to be called when its value changes.

>>> from sunset import Key

>>> number_of_ponies = Key(default=0)
>>> def callback(value):
...     print("Pony count updated:", value)
>>> number_of_ponies.onValueChangeCall(callback)
>>> number_of_ponies.set(6)
Pony count updated: 6
True

Requirements

• Python 3.9 or later.
• If installing from sources:
  • The flit build tool.

Installation

Installing from PyPI (recommended)

Run:

pip install SunsetSettings

This will install the latest version of SunsetSettings, with its required dependencies.

Installing from sources

1. Download the code:

   git clone https://github.com/pvaret/SunsetSettings
   

2. Install the library:

   cd SunsetSettings ; flit install
   

That's it.

API documentation

The API documentation is available at https://sunsetsettings.readthedocs.io/.