How to refactor Python "switch statement"

Question

I'm refactoring some code that a friend wrote and recently stumbled across this function:

def setup_parameters(self, data):
    '''Parse raw data to determine game settings.'''
    for line in data.split('\n'):
      line = line.strip().lower()
      if line:
        tokens = line.split()

        self.L.debug("tokens: " + str(tokens))

        key = tokens[0]
        if key == 'cols':
          self.width = int(tokens[1])
        elif key == 'rows':
          self.height = int(tokens[1])
        elif key == 'player_seed':
          random.seed(int(tokens[1]))
        elif key == 'turntime':
          self.turntime = int(tokens[1])
        elif key == 'loadtime':
          self.loadtime = int(tokens[1])
        elif key == 'viewradius2':
          self.viewradius2 = int(tokens[1])
        elif key == 'attackradius2':
          self.attackradius2 = int(tokens[1])
        elif key == 'spawnradius2':
          self.spawnradius2 = int(tokens[1])

As you can see, there is a nasty kind of switch statement here, that clearly calls for a dictionary. I'm tempted to write this as a class dictionary since the keys are constant, but since the keys map to attributes of an instance (ie, 'cols': self.width) this doesn't compile.

My question is then, what is the right way to refactor such code?

Answer 1

Map the keys to the names of the attributes, and use setattr(self, attribute_name, int(tokens[1]) to set the value. E.g.:

attribute_dict = dict(cols="width", rows="height", turntime="turntime", ...)
[...]
value = int(tokens[1])
if key == "player_seed":
    random.seed(value)
else:
    setattr(self, attribute_dict[key], value)

Answer 2

You can build up a dictionary with the keys as accessors and lambda functions to execute the code for each key.

Answer 3

setup a dict with actions like

actions = dict(cols = lambda tokens: setattr(self, "width", int(tokens[1]), ... 
               player_seed = lambda tokens: random.seed(int(tokens[1]))
              )

and then:

 actions[key](tokens)