ThatWay

Thatway is a simple, decentralized configuration manager.

Place your configuration settings throughout your application--not in a centralized file or submodule--and thatway collects them and allows you to modify them through configurations files. Decentralized configuration reduces the complexity of submodules and the coupling between submodules.

Quickstart

1. Create a package with settings.

   examples/mypkg/moduleA/file.py

   from thatway import Setting
   
   
   class FirstClass:
       my_attribute = Setting(True, desc="Whether 'my_attribute' is an attribute")
   
       max_instances = Setting(3, desc="Maximum number of instances")

   examples/mypkg/moduleB/file.py

   from thatway import config, Setting
   
   config.moduleB.msg = Setting("This is my message")

2. View settings:

   import examples.mypkg
   from thatway import config
   
   print(config.dumps_yaml())

   FirstClass:
     my_attribute: true  # Whether 'my_attribute' is an antribue
     max_instances: 3  # Maximum number of instances
   moduleB:
     msg: This is my message

3. Load different settings:

   examples/mypkg/new_settings.yaml

   FirstClass:
     my_attribute: false
     max_instances: 2

   with python:

   from pathlib import Path
   import examples.mypkg
   from thatway import config
   
   config.load_yaml(str(Path("examples") / "mypkg" / "new_settings.yaml"))
   print(config.dumps_yaml())

   FirstClass:
     my_attribute: false  # Whether 'my_attribute' is an antribue
     max_instances: 2  # Maximum number of instances
   moduleB:
     msg: This is my message

Rules

The following are design decisions on the behavior of thatway's configuration manager.

1. Configure directly

   Settings can be set directly on the config object.

   >>> from thatway import config, Setting
   >>> config.a = Setting(3)
   >>> config.a
   3
   >>> config.nested.b = Setting("nested")
   >>> config.nested.b
   'nested'

   Trying to set an entry in the config without a setting raises an exception.

   >>> from thatway import config
   >>> config.new_value = 3
   Traceback (most recent call last):
   ...
   thatway.base.ConfigException: Only Settings can be inserted in the Config

2. Configure object attributes

   Settings can be set as object attributes.

   >>> from thatway import Setting
   >>> class Obj:
   ...     attribute = Setting("my value")
   >>> obj = Obj()
   >>> obj.attribute
   'my value'

3. Configuration locking

   Settings cannot be accidentally modified. Once they're set, they're set until the config's update or load methods are used.

   >>> from thatway import Setting
   >>> config.b = Setting(3)
   >>> config.b
   3
   >>> config.b = Setting(5)  # oops!
   Traceback (most recent call last):
   ...
   thatway.base.ConfigException: Entry 'b' already in the Config--use a Config.update or load method to change its value.
   >>> config.b = 5  # oops!
   Traceback (most recent call last):
   ...
   thatway.base.ConfigException: Only Settings can be inserted in the Config
   >>> config.update({'b': 5})
   >>> config.b
   5

   The one exception is that settings defined on a class can be replaced on the class itself--not a class instance. This is because settings act as descriptors for classes.

4. Type Enforcement

   Setting types are checked and maintained with either the setting's value type, or the allowed_types optional argument.

   >>> from thatway import Setting
   >>> config.c = Setting(5, allowed_types=(int, str))
   >>> config.update({'c': 'my new c value'})
   >>> config.c
   'my new c value'
   >>> config.d = Setting(6)
   >>> config.update({'d': 'my new d value'})
   Traceback (most recent call last):
   ...
   ValueError: Could not convert 'my new d value' into any of the following types: [<class 'int'>]

5. Missing Settings

   Trying to update a setting that doesn't exist is not possible. This behavior is designed to avoid trying to change a setting but using an incorrect setting name and location.

   >>> from thatway import Setting
   >>> config.update({'e': 'unassigned'})  # 'f' doesn't exist in config
   Traceback (most recent call last):
   ...
   KeyError: "Tried assigning setting with name 'e' which does not exist in the Config"

6. Immutable Settings Values

   Setting values can only be immutable objects.

   >>> from thatway import Setting
   >>> config.cli.color = Setting(True)
   >>> config.cli.default_filenames = Setting(('a.html', 'b.html'))
   >>> config.cli.value_list = Setting([1, 2])  # lists are mutable
   Traceback (most recent call last):
   ...
   thatway.base.ConfigException: Setting value '[1, 2]' must be immutable

Features

1. Setting descriptions

   Settings can include descriptions.

   >>> from thatway import Setting
   >>> config.e = Setting(4, desc="The 'e' attribute")

2. Yaml processing. Settings can be dumped in yaml with config.dumps_yaml().

   Obj:
     a: 1
   b: name  # The 'b' setting
   nested:
     c: true

   And yaml strings or files can be loaded with config.loads_yaml(string) and config.load_yaml(filepath), respectively.

3. Toml processing

   Settings can be dumped in toml with config.dumps_toml().

   [Obj]
     a = 1
   b = "name"  # The 'b' setting
   [nested]
     c = true

   And toml strings or files can be loaded with config.loads_toml(string) and config.load_toml(filepath), respectively.