Interpolation Options

The interpolation system can handles replacement on the fly. This is done within the options themselves, as well as during migrations.

At its most basic, interpolation allows you to have a string that contains a key string that is replaced with the value of another configuration option. For example:

::

# setup the configuration manager

config = ConfigManager() config.add(‘section1’) section1 = config[‘section1’]

# add some options for the data directory and data file

section1[‘data_dir’] = ‘my_path/data’ section1[‘data_filename’] = ‘my_data_file.db’

# add an option that will return the full file and path for the database:

section1[‘database’] = ‘%(data_dir)/%(data_filename)’

# when you call the interpolated option section1[‘database’]

‘mypath/data/my_data_file.db’

..note:: there are better approaches to handling paths in the system that woudl work better with cross platform systems,

see :py:module:`pathlib`

Interpolation can also handle cross section variables, so you can use %(section_name.option_name) if needed, as well as recursive variables where you are including a interpolated option in another interpolated option (up to a max of 10 levels).

if you need to use “%” in your option values, you can use escape it with “%%”

..note:: you can disable interpolation by passing None to the “interpolator” keyward arg for the ConfigManager