code: def interpolate_sysenv(line, defaults={}):
      '''
      Format line system environment variables + defaults
      '''
      map = ChainMap(os.environ, defaults)
      return line.format(**mapf interpolate_sysenv(line, defaults={}):
      '''
      Format line system environment variables + defaults
      '''
      map = ChainMap(os.environ, defaults)
      return line.format(**map)
docs: Format line system environment variables + defaults