Dinner Table Guest from A.K. Dewdney's simulation

guest.py

class Guest(object):
    def __init__(self, name, index, x, y, ideal_distances):
        self.name = name
        self.index = index
        self.x = x
        self.y = y
        self.target_x = x
        self.target_y = y
        self.ideal_distances = ideal_distances
        self.presum = 0
        self.sum = 0

    def update(self, guests):
      self.presum = self.sum
      self.sum = 0

      for i in range(8):
        otherGuest = guests[i]
        distance = self.distanceTo(otherGuest)
        self.sum += abs( distance - self.ideal_distances[i])
        if (self.sum < self.presum):
          self.target_x = otherGuest.x
          self.target_y = otherGuest.y


      if (self.target_x > self.x):
        self.x += 1
      if (self.target_x < self.x):
        self.x -= 1
      if (self.target_y > self.y):
        self.y += 1
      if (self.target_y < self.y):
        self.y -= 1
          # TODO need to translate the distance algorithm on page 156
          # TODO need to figure out keeping guests from walking through tables or walls
          # self.x += translate(self.target_x - self.x, 0, 30, -1, 1)
          # self.y += translate(self.target_y - self.y, 0, 30, -1, 1)

    def distanceTo(self, otherGuest):
      return math.sqrt(math.pow( self.x - otherGuest.x, 2) + math.pow( self.y - otherGuest.y, 2))

    def __repr__(self):
      tmpl = Template("$name is at: [$x,$y] and has target of [$target_x][$target_y]")
      return tmpl.substitute(name=self.name, x=self.x, y=self.y, target_x=self.target_x, target_y=self.target_y)