Config system

config_system.md

Requirements

• access config['axes.xticks.color'] and config.axes.xticks.color. Which one is the preferred? Or both?
• validators
• default values? resetting?
• virtual or real hierarchy: Is the structure only naming convention or do we want to define explicit structure components?
• support aliases, possibility for deprecated aliases
• simple layering of configs (ChainMap-like?)
• Definition of values should be explicit (e.g. ArgumentParser-style)
  config.add_param('lines.width', type=float, description="The width of all lines in points")
• option for inferred values ("grid.linewidth" should use the value from "lines.width")
• fast access - may be needed often in constructors for 'small' objects like ticks.
• contexts

To clarify

How do other libraries handle this? numpy, scipy, scikit image, pandas,

• numpy: n/a
• scipy: n/a
• pandas: http://pandas.pydata.org/pandas-docs/stable/user_guide/options.html
  • Naming: option/options
  • "fully-dotted"
  • Supports both pd.options.display.max_rows and get_option('pd.options.display.max_rows')
  • Has a regexp matcher for names Would not do this because
    • ambiguity
    • may introduce unnoticed errors
    • uniqueness may fail when more options are added
  • case insensitive
  • MATLABian context style with option_context('display.max_rows', 10, 'display.max_columns', 5):
• scikit image: n/a
• flask: http://flask.pocoo.org/docs/1.0/api/#flask.Config
  • dict extended for reading/writing config files
  • Parameter names: UNDERSCORE_SEPARATED
  • get_namespace() for returning
• django: https://docs.djangoproject.com/en/2.2/topics/settings/
  • a settings module with uppercase variables
  • not recommended to change at runtime
• ipython: https://ipython.readthedocs.io/en/stable/config/intro.html https://github.com/ipython/ipython/blob/a2685d78f2403f84e6cb915ae11a4f6033ccc5f6/docs/source/development/config.rst
  • Using its own traitlets variant and traitlets.config https://github.com/ipython/traitlets/tree/master/traitlets/config

validators:

• types: assert isinstance(x, type)
• lists: assert x in list
• callable: assert func(x)
• preprocessor x = func(x)

Context API variants

with config({'axes.xticks.color': 'red', 'axes.xticks.edgewidth': 4}):

with config({'axes.xticks': {'color': 'red', 'edgewidth': 4}}):

with config(axes_xticks_color='red', axes_xticks_edgewidth=4}):