Variable Substitution

Since trafaret-config 2.0 environment variables in the config are replaced by default, this means that config like this:

url: http://${HOST}:$PORT/

Will get HOST and PORT variables insert from the environment, and if variable does not exist, you will get the following error:

config.yaml:2: variable 'PORT' not found
  -> 'http://${HOST}:$PORT/'

To override variables that are subsituted pass vars={'some': 'dict'} to any of the functions:

• config_from_options(..., vars=custom_vars)
• read_and_validate(..., vars=custom_vars)
• parse_and_validate(..., vars=custom_vars)

To turn off variable substitution at all pass vars=None

Sometimes you might want to print variables used in configuration file, i.e. to make some configuration file inter. If you’re using trafaret_config.commandline you can do it using default command-line argument:

$ ./run.py --print-config-vars
HOST
PORT