Merge pull request #73 from ASPP/feature/graph-attribute

use the newly introduced `bot.graph` attribute

README.md

@@ -318,11 +318,13 @@ Note that the `Bot` object is read-only, i.e. any modifications you make to that
     (3, 9) in bot.walls
     ```
 
-    The maze can be represented as a graph. If you want to use [networkx](https://networkx.github.io) for shortest path algorithms, you can use the `walls_to_graph` function in `pelita.utils`.
+    The maze is also represented as a graph in the attribute `bot.graph`.
 
-    Examples for using a graph representation for shortest path calculations can be found in [demo04_basic_attacker.py](demo04_basic_attacker.py) and [demo05_basic_defender.py](demo05_basic_defender.py).
-
-- **`bot.shape`** is a tuple with the size of the maze. The ususal maze size will be `32x16`, that is `(32, 16)`, unless other layouts are specified.
+- **`bot.graph`** is a representation of the maze as a graph. The graph represents the free squares in the maze –i.e. all the non-wall coordinates– and their connections. The `bot.graph` object is an instance of the [`Graph`](https://networkx.org/documentation/stable/reference/classes/graph.html) class from the  [networkx](https://networkx.github.io) library. `bot.graph` is immutable: an editable copy of the graph is returned by the `bot.graph.copy()` method if you need it. 
+
+    Examples for using a graph representation for shortest path calculations using the [networkx](https://networkx.github.io) library can be found in [demo04_basic_attacker.py](demo04_basic_attacker.py) and [demo05_basic_defender.py](demo05_basic_defender.py).
+ 
+- **`bot.shape`** is a tuple with the size of the maze. The usual maze size will be `32x16`, that is `(32, 16)`, unless other layouts are specified.
 
 - **`bot.homezone`** is a tuple of all the coordinates of your side of the maze that are not a wall. If for example you are the red team in a `32×16` maze, your homezone might be:
     ```python

demo04_basic_attacker.py

@@ -6,9 +6,6 @@
 
 import networkx
 
-from pelita.utils import walls_to_graph
-
-
 TEAM_NAME = 'Basic Attacker Bots'
 
 def init_attack_state():
@@ -25,9 +22,6 @@ def move(bot, state):
         # food targets.
         state[0] = init_attack_state()
         state[1] = init_attack_state()
-        # Initialize a graph representation of the maze.
-        # This can be shared among our bots.
-        state['graph'] = walls_to_graph(bot.walls)
 
     # define a few variables for less typing
     enemy = bot.enemy
@@ -42,7 +36,7 @@ def move(bot, state):
         target = bot.random.choice(enemy[0].food)
         # use networkx to get the shortest path from here to the target
         # we do not use the first position, which is always equal to bot_position
-        path = networkx.shortest_path(state['graph'], bot.position, target)[1:]
+        path = networkx.shortest_path(bot.graph, bot.position, target)[1:]
         state[bot.turn]["attack_path"] = path
         state[bot.turn]["attack_target"] = target
 

demo05_basic_defender.py

@@ -7,8 +7,6 @@
 
 import networkx
 
-from pelita.utils import walls_to_graph
-
 
 TEAM_NAME = 'Basic Defender Bots'
 
@@ -20,8 +18,6 @@ def init_defend_state():
 
 def move(bot, state):
     if state == {}:
-        # store the graph representation of the maze in the state object
-        state['graph'] = walls_to_graph(bot.walls)
         state[0] = init_defend_state()
         state[1] = init_defend_state()
 
@@ -39,7 +35,7 @@ def move(bot, state):
         raise Exception('We should never be here!')
 
     # get the next position along the shortest path to our target enemy bot
-    next_pos = networkx.shortest_path(state['graph'], bot.position, target)[1]
+    next_pos = networkx.shortest_path(bot.graph, bot.position, target)[1]
     # we save the current target in our state dictionary
     state[bot.turn]["defend_target"] = target
 

demo06_switching_bots.py

@@ -4,8 +4,6 @@
 # strategy. Once the attacking bot is killed, it restarts as a defender, while
 # the previous defender changes its personality and becomes the new attacker.
 
-from pelita.utils import walls_to_graph
-
 from demo05_basic_defender import move as move_defender
 from demo04_basic_attacker import move as move_attacker
 
@@ -34,9 +32,7 @@ def move(bot, state):
     # (and each of the functions only works with “their” prefixed version).
 
     if state == {}:
-        # here each bot has its own state dictionary (0 and 1) and they share
-        # the same game state information in the "graph"
-        state['graph'] = walls_to_graph(bot.walls)
+        # here each bot has its own state dictionary (0 and 1)
         state[0] = init_state("attacker")
         state[1] = init_state("defender")