Minor changes for Python 3.x

Oops fixed

Adding in WolfSheepPredation

Adding parameters and fixing style issues

Author: dmasad

examples/Schelling.py

@@ -19,7 +19,7 @@
     viz.step_forward(10)
 '''
 
-from __future__ import division # We're doing this in Python 2.x, right?
+from __future__ import division # For Python 2.x compatibility
 import random
 
 from mesa import Model, Agent

examples/WolfSheep/WolfSheep.py

@@ -0,0 +1,144 @@
+'''
+Wolf-Sheep Predation Model
+================================
+
+Replication of the model found in NetLogo:
+    Wilensky, U. (1997). NetLogo Wolf Sheep Predation model. 
+    http://ccl.northwestern.edu/netlogo/models/WolfSheepPredation. 
+    Center for Connected Learning and Computer-Based Modeling, 
+    Northwestern University, Evanston, IL.
+
+TODO: Implement grass
+'''
+
+import random
+
+from mesa import Model, Agent
+from mesa.space import MultiGrid
+from mesa.time import Random_Activation
+
+from RandomWalk import RandomWalker
+
+class WolfSheepPredation(Model):
+    '''
+    Wolf-Sheep Predation Model
+    '''
+
+    initial_sheep = 100
+    initial_wolves = 50
+    sheep_gain_from_food = 4
+
+    grass = False
+
+    wolf_gain_from_food = 20
+    sheep_reproduce = 0.04
+    wolf_reproduce = 0.05
+
+    height = 20
+    width = 20
+
+    def __init__(self, height=20, width=20, 
+                    initial_sheep=100, initial_wolves=50, sheep_reproduce=0.04,  
+                    wolf_reproduce=0.05, wolf_gain_from_food=20, 
+                    grass=False, sheep_gain_from_food=4):
+        '''
+        Create a new Wolf-Sheep model with the given parameters.
+
+        Args:
+            initial_sheep: Number of sheep to start with
+            initial_wolves: Number of wolves to start with
+            sheep_reproduce: Probability of each sheep reproducing each step
+            wolf_reproduce: Probability of each wolf reproducing each step
+            wolf_gain_from_food: Energy a wolf gains from eating a sheep
+            grass: Whether to have the sheep eat grass for energy
+            sheep_gain_from_food: Energy sheep gain from grass, if enabled.
+        '''
+        
+        # Set parameters
+        self.height = height
+        self.width = width
+        self.initial_sheep = initial_sheep
+        self.initial_wolves = initial_wolves
+        self.sheep_reproduce = sheep_reproduce
+        self.wolf_reproduce = wolf_reproduce
+        self.wolf_gain_from_food = wolf_gain_from_food
+        self.grass = grass
+        self.sheep_gain_from_food = sheep_gain_from_food
+        
+        self.schedule = Random_Activation(self)
+        self.grid = MultiGrid(self.height, self.width, torus=True)
+
+        # Create sheep:
+        for i in range(self.initial_sheep):
+            x = random.randrange(self.width)
+            y = random.randrange(self.height)
+            sheep = Sheep(self.grid, x,  y, True)
+            self.grid[y][x].add(sheep)
+            self.schedule.add(sheep)
+
+        # Create wolves
+        for i in range(self.initial_wolves):
+            x = random.randrange(self.width)
+            y = random.randrange(self.height)
+            energy = random.randrange(2 * self.wolf_gain_from_food)
+            wolf = Wolf(self.grid, x,  y, True, energy)
+            self.grid[y][x].add(wolf)
+            self.schedule.add(wolf)
+
+    def step(self):
+        self.schedule.step()
+
+
+class Sheep(RandomWalker, Agent):
+    '''
+    A sheep that walks around, reproduces (asexually) and gets eaten.
+
+    The init is the same as the RandomWalker.
+    '''
+
+    def step(self, model):
+        '''
+        A model step. Move, then eat grass and reproduce.
+        '''
+        self.random_move()
+        if random.random() < model.sheep_reproduce:
+            # Create a new sheep:
+            lamb = Sheep(self.grid, self.x, self.y, self.moore)
+            model.grid[self.y][self.x].add(lamb)
+            model.schedule.add(lamb)
+
+
+class Wolf(RandomWalker, Agent):
+    '''
+    A wolf that walks around, reproduces (asexually) and eats sheep.
+    '''
+
+    energy = None
+
+    def __init__(self, grid, x, y, moore, energy):
+        super().__init__(grid, x, y, moore)
+        self.energy = energy
+
+
+    def step(self, model):
+        self.random_move()
+        self.energy -= 1
+
+        # If there are sheep present, eat one
+        this_cell = model.grid[self.y][self.x]
+        sheep = [obj for obj in this_cell if isinstance(obj, Sheep)]
+        if len(sheep) > 0:
+            sheep_to_eat = random.choice(sheep)
+            self.energy += model.wolf_gain_from_food
+
+            # Kill the sheep
+            model.grid[self.y][self.x].remove(sheep_to_eat)
+            model.schedule.remove(sheep_to_eat)
+
+        # Reproduction:
+        if random.random() < model.wolf_reproduce:
+            # Create a new wolf cub
+            cub = Wolf(self.grid, self.x, self.y, self.moore, self.energy/2)
+            self.energy = self.energy/2
+            model.grid[self.y][self.x].add(cub)
+            model.schedule.add(cub)

examples/WolfSheep/WolfSheepVisualization.py

@@ -0,0 +1,30 @@
+'''
+Visualization for the Wolf-Sheep Predation
+'''
+
+from WolfSheep import Wolf, Sheep
+from mesa.visualization.TextVisualization import TextVisualization, TextData, TextGrid
+
+class WolfSheepVisualization(TextVisualization):
+    '''
+    ASCII visualization of the WolfSheepPredation model.
+
+    Each cell displays S if only sheep, W if only wolves, or X if both.
+    (blank if none)
+    '''
+
+    def __init__(self, model):
+        self.model = model
+        grid_viz = TextGrid(self.model.grid, self.draw_cell)
+        self.elements = [grid_viz]
+
+    @staticmethod
+    def draw_cell(cell):
+        if len(cell) == 0:
+            return " "
+        if len([obj for obj in cell if isinstance(obj, Sheep)]) == len(cell):
+            return "S"
+        if len([obj for obj in cell if isinstance(obj, Wolf)]) == len(cell):
+            return "W"
+        else:
+            return "X"

examples/WolfSheep/__init__.py

@@ -0,0 +1,6 @@
+from WolfSheep import WolfSheepPredation
+from WolfSheepVisualization import WolfSheepVisualization
+
+if __name__ == "__main__":
+	model = WolfSheepPredation()
+	viz = WolfSheepVisualization(model)

mesa/visualization/TextVisualization.py

@@ -53,7 +53,7 @@ def render(self):
         Render all the text elements, in order.
         '''
         for element in self.elements:
-            print element
+            print(element)
 
     def step(self):
         '''