Add radius argument to NetworkGrid.get_neighbors() (#1973)

For some reason get_neighborhood() did have the radius argument, but get_neighbors() did not have it in the NetworkGrid. This commit resolves that inconsistency and allows get_neighbors() to take a radius as input and return the agents in that radius. Tests are included.

mesa/space.py

@@ -1539,9 +1539,11 @@ def get_neighborhood(
             neighborhood = sorted(neighbors_with_distance.keys())
         return neighborhood
 
-    def get_neighbors(self, node_id: int, include_center: bool = False) -> list[Agent]:
-        """Get all agents in adjacent nodes."""
-        neighborhood = self.get_neighborhood(node_id, include_center)
+    def get_neighbors(
+        self, node_id: int, include_center: bool = False, radius: int = 1
+    ) -> list[Agent]:
+        """Get all agents in adjacent nodes (within a certain radius)."""
+        neighborhood = self.get_neighborhood(node_id, include_center, radius)
         return self.get_cell_list_contents(neighborhood)
 
     def move_agent(self, agent: Agent, node_id: int) -> None:

tests/test_space.py

@@ -867,12 +867,54 @@ def test_agent_positions(self):
             a = self.agents[i]
             assert a.pos == pos
 
-    def test_get_neighbors(self):
+    def test_get_neighborhood(self):
         assert len(self.space.get_neighborhood(0, include_center=True)) == 3
         assert len(self.space.get_neighborhood(0, include_center=False)) == 2
         assert len(self.space.get_neighborhood(2, include_center=True, radius=3)) == 7
         assert len(self.space.get_neighborhood(2, include_center=False, radius=3)) == 6
 
+    def test_get_neighbors(self):
+        """
+        Test the get_neighbors method with varying radius and include_center values. Note there are agents on node 0, 1 and 5.
+        """
+        # Test with default radius (1) and include_center = False
+        neighbors_default = self.space.get_neighbors(0, include_center=False)
+        self.assertEqual(
+            len(neighbors_default),
+            1,
+            "Should have 1 neighbors with default radius and exclude center",
+        )
+
+        # Test with default radius (1) and include_center = True
+        neighbors_include_center = self.space.get_neighbors(0, include_center=True)
+        self.assertEqual(
+            len(neighbors_include_center),
+            2,
+            "Should have 2 neighbors (including center) with default radius",
+        )
+
+        # Test with radius = 2 and include_center = False
+        neighbors_radius_2 = self.space.get_neighbors(0, include_center=False, radius=5)
+        expected_count_radius_2 = 2
+        self.assertEqual(
+            len(neighbors_radius_2),
+            expected_count_radius_2,
+            f"Should have {expected_count_radius_2} neighbors with radius 2 and exclude center",
+        )
+
+        # Test with radius = 2 and include_center = True
+        neighbors_radius_2_include_center = self.space.get_neighbors(
+            0, include_center=True, radius=5
+        )
+        expected_count_radius_2_include_center = (
+            3  # Adjust this based on your network structure
+        )
+        self.assertEqual(
+            len(neighbors_radius_2_include_center),
+            expected_count_radius_2_include_center,
+            f"Should have {expected_count_radius_2_include_center} neighbors (including center) with radius 2",
+        )
+
     def test_move_agent(self):
         initial_pos = 1
         agent_number = 1