title: IndexError: list index out of range in a matrix
body: <p>I've been trying to create a Procedurally Generated Dungeon, as seen in <a href="http://www.gamasutra.com/blogs/AAdonaac/20150903/252889/Procedural_Dungeon_Generation_Algorithm.php" rel="nofollow">this article</a>. But that was a little to hard for me to understand the working this type of algorithm. So instead, I've been using <a href="https://gamedevelopment.tutsplus.com/tutorials/create-a-procedurally-generated-dungeon-cave-system--gamedev-10099" rel="nofollow">this</a> as a guide to at least understand the room placement.</p>
  
  <p>The program used in the article is made in Java, so I made some adaptations to my "reality", and tried to emulate the same results in Python 3.5.</p>
  
  <p>My code is as follows:</p>
  
  <pre><code>from random import randint
  
  
  class Room:
  
      """docstring for Room"""
  
      def __init__(self, x, y, w, h):
          """[summary]
  
          [description]
  
          Arguments:
                  x {int} -- bottom-left horizontal anchorpoint of the room
                  y {int} -- bottom-left vertical anchor point of the room
                  w {int} -- width of the room
                  h {int} -- height of the room
          """
          self.x1 = x
          self.x2 = x + w
          self.y1 = y
          self.y2 = y + h
          self.w = w
          self.h = h
          self.center = ((self.x1 + self.x2)/2, (self.y1 + self.y2)/2)
  
      def intersects(self, room):
          """[summary]
  
          Verifies if the rooms overlap
  
          Arguments:
                  room {Room} -- a room object
          """
          return(self.x1 &lt;= room.x2 and self.x2 &gt;= room.x1 and \
                 self.y1 &lt;= room.y2 and self.y2 &gt;= room.y1)
  
      def __str__(self):
          room_info = ("Coords: (" + str(self.x1) + ", " + str(self.y1) +
                       ") | (" + str(self.x2) + ", " + str(self.y2) + ")\n")
          room_info += ("Center: " + str(self.center) + "\n")
          return(room_info)
  
  MIN_ROOM_SIZE = 10
  MAX_ROOM_SIZE = 20
  MAP_WIDTH = 400
  MAP_HEIGHT = 200
  MAX_NUMBER_ROOMS = 20
  
  dungeon_map = [[None] * MAP_WIDTH for i in range(MAP_HEIGHT)]
  # print(dungeon_map)
  
  
  def crave_room(room):
      """[summary]
  
      "saves" a room in the dungeon map by making everything inside it's limits 1
  
      Arguments:
              room {Room} -- the room to crave in the dungeon map
      """
      for x in xrange(min(room.x1, room.x2), max(room.x1, room.x2) + 1):
          for y in xrange(min(room.y1, room.y2), max(room.y1, room.y2) + 1):
              print(x, y)  # debug
              dungeon_map[x][y] = 1
      print("Done")  # dungeon
  
  
  def place_rooms():
  
      rooms = []
  
      for i in xrange(0, MAX_NUMBER_ROOMS):
          w = MIN_ROOM_SIZE + randint(0, MAX_ROOM_SIZE - MIN_ROOM_SIZE + 1)
          h = MIN_ROOM_SIZE + randint(0, MAX_ROOM_SIZE - MIN_ROOM_SIZE + 1)
          x = randint(0, MAP_WIDTH - w) + 1
          y = randint(0, MAP_HEIGHT - h) + 1
  
          new_room = Room(x, y, w, h)
          fail = False
          for other_room in rooms:
              if new_room.intersects(other_room):
                  fail = True
                  break
          if not fail:
              print(new_room)
              crave_room(new_room)  # WIP
              new_center = new_room.center
              # rooms.append(new_room)
              if len(rooms) != 0:
                  prev_center = rooms[len(rooms) - 1].center
  
                  if(randint(0, 1) == 1):
                      h_corridor(prev_center[0], new_center[0], prev_center[1])
                      v_corridor(prev_center[1], new_center[1], prev_center[0])
                  else:
                      v_corridor(prev_center[1], new_center[1], prev_center[0])
                      h_corridor(prev_center[0], new_center[0], prev_center[1])
          if not fail:
              rooms.append(new_room)
      for room in rooms:
          print(room)
  
  
  def h_corridor(x1, x2, y):
      for x in xrange(min(x1, x2), max(x1, x2) + 1):
          dungeon_map[x][y] = 1
  
  
  def v_corridor(y1, y2, x):
      for y in xrange(min(y1, y2), max(y1, y2) + 1):
          dungeon_map[x][y] = 1
  
  place_rooms()
  </code></pre>
  
  <p>but whenever I run it, I get the following error:</p>
  
  <pre><code>Traceback (most recent call last):
    File "/home/user/dungeon.py", line 114, in &lt;module&gt;
      place_rooms()
    File "/home/user/dungeon.py", line 87, in place_rooms
      crave_room(new_room)  
    File "/home/user/dungeon.py", line 65, in crave_room
      dungeon_map[x][y] = 1
  IndexError: list index out of range
  </code></pre>
  
  <p>For what I understood from my code, the <code>crave_room</code> function should work correctly, since I'm using the <code>min</code> and <code>max</code> functions. And since the <code>h_corridor</code> and <code>v_corridor</code> functions work in a similar way They present the same kind of problem.</p>
  
  <p>I'm not sure if the problem is happening due the fact that I'm using a matrix as a substitute to the canvas used in the original article. I was suspecting a local/global variable problem, but I don't think that's the problem. I'm afraid I'm making a very stupid mistake and not seeing it.</p>
  
  <p>Any code improvement tips or suggestions about better data structures to use will be welcome, and if anyone has, a more clearer/simpler article in the subject, preferably on Python, I saw a lot of the related posts in here, but I'm still kind of lost.</p>
  
  <p>Thanks for any help. :D</p>