Because I dislike all the other python config libraries, and it shouldn't have to be hard.

All I wanted was a config system that:

• Was easy to set up
• Was easy to mock/test
• Was easy to get values out of
• Was easy for end users to write configuration for
• Was easy to supply defaults to

This config system allows the user to specify configs in the following ways:

• As an environment variable for each config lineitem
• As a yaml configuration file specified on the command line
• As a default yaml filename in their ~/.config directory
• As default values provided by the application developer

It tries each of these in order until it finds one.

Restrictions: If you want to use environment variables to override settings, keep your yaml files flat and have all values be strings.

I haven't put it on pypi or even github, but it'll be something like

pip install git+https://github.com/buchuki/real_simple_config.git

To set up configuration, call init_config like so:

    import real_simple
    real_simple.init_config(
        user_config,
        'my_app_default_config.yaml',
        'MYAPP_',
        {
            'FOO': 'def_value',
            'BAR': ''})

Where:

• user_config is an optional filename the user passed to you on the command line using your preferred command parsing library.
• my_app_default_config.yaml is the name of a file you want the user to read from in ~/.config if they didn't explicitly pass a config file.
• MYAPP_ is a prefix for environment variable lookup. Any key in the default dictionary can be looked up from a command-line with export MYAPP_FOO='my_val'.
• The dictionary is the list of default values for the configuration. Any key not in this dictionary will not be looked up in the user's config files or environment. So set defaults to None if you require the user to look them up.

To look up a configuration value, use:

    from real_simple import conf
    val = conf('FOO')

You can mock out real_simple.init_config or real_simple.CONFIGURATION depending on your needs. The former would be mocked if your test code is called before your app has called init_config. The latter would be mocked if you want to specify mocked config values after init_config has been called. The latter is the most likely case.