refactor: Simplify Schelling code (#222)

* refactor: Simplify Schelling code

1. Remove unused model attributes
2. Make `similar` calculation more natural language readable

* Remove unused argument doc

* Add type hints to agent class

* refactor: Simplify self.running expression

Author: rht

examples/schelling/model.py

@@ -6,24 +6,21 @@ class SchellingAgent(mesa.Agent):
     Schelling segregation agent
     """
 
-    def __init__(self, model, agent_type):
+    def __init__(self, model: mesa.Model, agent_type: int) -> None:
         """
         Create a new Schelling agent.
 
         Args:
-           x, y: Agent initial location.
            agent_type: Indicator for the agent's type (minority=1, majority=0)
         """
         super().__init__(model)
         self.type = agent_type
 
-    def step(self):
-        similar = 0
-        for neighbor in self.model.grid.iter_neighbors(
+    def step(self) -> None:
+        neighbors = self.model.grid.iter_neighbors(
             self.pos, moore=True, radius=self.model.radius
-        ):
-            if neighbor.type == self.type:
-                similar += 1
+        )
+        similar = sum(1 for neighbor in neighbors if neighbor.type == self.type)
 
         # If unhappy, move:
         if similar < self.model.homophily:
@@ -60,10 +57,6 @@ def __init__(
         """
 
         super().__init__(seed=seed)
-        self.height = height
-        self.width = width
-        self.density = density
-        self.minority_pc = minority_pc
         self.homophily = homophily
         self.radius = radius
 
@@ -79,8 +72,8 @@ def __init__(
         # the coordinates of a cell as well as
         # its contents. (coord_iter)
         for _, pos in self.grid.coord_iter():
-            if self.random.random() < self.density:
-                agent_type = 1 if self.random.random() < self.minority_pc else 0
+            if self.random.random() < density:
+                agent_type = 1 if self.random.random() < minority_pc else 0
                 agent = SchellingAgent(self, agent_type)
                 self.grid.place_agent(agent, pos)
 
@@ -95,5 +88,4 @@ def step(self):
 
         self.datacollector.collect(self)
 
-        if self.happy == len(self.agents):
-            self.running = False
+        self.running = self.happy != len(self.agents)