Variable expansion

expansion.py

# Another idea, you could avoid any "custom language" / parsing / regex stuff by just referencing 
# variables by ID an having them provide valid python strings that have format placeholders

# documentation on the string.format function: https://www.geeksforgeeks.org/python-format-function/

json = {
  'variables': {
    'foo': 'asdf',
    'bar': 'fdsa'
  },
  'expressions': [
    {
      'text': 'my cool string {}, it has variables {}'
      'variables': ['foo', 'bar']
  ]
}

for expression in json["expressions"]:
  # first get the value for each of the variables in the expression
  # (in your real script you'll obviously need to do this more dynamically
  variable_values = [
    json['variables'][expression['variables'][0]],
    json['variables'][expression['variables'][1]]
  ]
  # then provide them as argument to the format function and you're good to go
  replaced_text = expression['text'].format(*variable_values)
  # 'my cool string asdf, it has variables fdsa'