s3ttings 0.0.7

Setting

1  import asyncio
2  from settings import Setting
3 
4  timeout = Setting(f"{__name__}.io.timeout", default=5)
5 
6  async def main():
7      with asyncio.timeout(timeout.value):
8          await long_running_task()

Settings can be tweaked:

 1  from settings import Setting
 2 
 3  timeout = Setting(f"{__name__}.io.timeout", default=5)
 4 
 5  if __name__ == "__main__":
 6      assert timeout.value == 5
 7 
 8      timeout.value = 3
 9      assert timeout.value = 3
10 
11      with timeout(10):
12          assert timeout.value == 10
13      assert timeout.value == 3
14 
15      del timeout.value
16      assert timeout.value == 5
17 
18      timeout.default = 6
19      assert timeout.value == 6
20 
21      del timeout.default
22      timeout.value  # raises `settings.NoDefaultValueError(timeout)`

They can transparently use other settings as their default:

1  from settings import Setting
2 
3  timeout = Setting(f"{__name__}.io.timeout", default=5)
4  load_timeout = Setting(f"{__name__}.io.load.timeout", default=timeout)
5  dump_timeout = Setting(f"{__name__}.io.dump.timeout", default=timeout)
6 
7  if __name__ == "__main__":
8      assert load_timeout.value == dump_timeout.value == timeout.value == 5

Finally, Setting implements the multiton pattern:

1  from settings import Setting
2 
3  timeout = Setting(f"{__name__}.io.timeout", default=5)
4 
5  if __name__ == "__main__":
6      assert Setting(f"{__name__}.io.timeout") is timeout

SettingTree

Collections of settings can be grouped in setting trees:

 1  from settings import Setting, SettingTree
 2 
 3  options = SettingTree(
 4      Setting(f"{__name__}.io.timeout", default=5),
 5      Setting(
 6          f"{__name__}.io.load.timeout", default=Setting(f"{__name__}.io.timeout")
 7      ),
 8      Setting(
 9          f"{__name__}.io.dump.timeout", default=Setting(f"{__name__}.io.timeout")
10      ),
11      prefix=__name__,
12  )
13 
14  if __name__ == "__main__":
15      assert options.io.timeout.value == 5

For large projects with many settings, a common practice is to define multiple trees and merge them together in the top-level module:

1  from settings import SettingTree
2 
3  from .a import options as _options_a
4  from .b import options as _options_b
5 
6  options = SettingTree(*_options_a, *_options_b, prefix=__name__)

EnvSetting

A subclass of Setting, EnvSetting can source default values from environment variables:

 1  import os
 2  from settings import EnvSetting
 3 
 4  timeout = EnvSetting("my.project.io.timeout", default=5, envparse=int)
 5 
 6  if __name__ == "__main__":
 7      assert timeout.value == 5
 8 
 9      os.environ["my.project.io.timeout"] = "10"
10      assert timeout.value == 10