Fix identity comparisons with literals and mutable default arguments

Replace `is`/`is not` comparisons with non-None literals (`==`/`!=`/`not`)
to fix SyntaxWarning in Python 3.12+ (related to #1291). Also replace
mutable default arguments (lists) with None or tuples to prevent shared
state bugs.

Identity comparisons fixed:
- `is not self.n_links` (integer) in 3 arm navigation files
- `state is WAIT_FOR_NEW_GOAL` (integer) in n_joint_arm_to_point_control.py
- `path_found is False` (bool literal) in probabilistic_road_map.py
- `flag is inside` (bool) in grid_map_lib.py

Mutable default arguments fixed:
- `obstacles=[]` -> `obstacles=None` in arm_obstacle_navigation.py and _2.py
- `start_vel=[0,0,0]` etc. -> tuples in TrajectoryGenerator.py
- `obstacle_avoid_points=[]` -> `None` in GridWithDynamicObstacles.py
- Removed mutable class-level list defaults in Grid class

Author: dhruvildarji

AerialNavigation/drone_3d_trajectory_following/TrajectoryGenerator.py

@@ -7,7 +7,7 @@
 import numpy as np
 
 class TrajectoryGenerator():
-    def __init__(self, start_pos, des_pos, T, start_vel=[0,0,0], des_vel=[0,0,0], start_acc=[0,0,0], des_acc=[0,0,0]):
+    def __init__(self, start_pos, des_pos, T, start_vel=(0,0,0), des_vel=(0,0,0), start_acc=(0,0,0), des_acc=(0,0,0)):
         self.start_x = start_pos[0]
         self.start_y = start_pos[1]
         self.start_z = start_pos[2]

ArmNavigation/arm_obstacle_navigation/arm_obstacle_navigation.py

@@ -244,16 +244,18 @@ def update_points(self):
 
         self.end_effector = np.array(self.points[self.n_links]).T
 
-    def plot(self, obstacles=[]):  # pragma: no cover
+    def plot(self, obstacles=None):  # pragma: no cover
         plt.cla()
+        if obstacles is None:
+            obstacles = []
 
         for obstacle in obstacles:
             circle = plt.Circle(
                 (obstacle[0], obstacle[1]), radius=0.5 * obstacle[2], fc='k')
             plt.gca().add_patch(circle)
 
         for i in range(self.n_links + 1):
-            if i is not self.n_links:
+            if i != self.n_links:
                 plt.plot([self.points[i][0], self.points[i + 1][0]],
                          [self.points[i][1], self.points[i + 1][1]], 'r-')
             plt.plot(self.points[i][0], self.points[i][1], 'k.')

ArmNavigation/arm_obstacle_navigation/arm_obstacle_navigation_2.py

@@ -275,16 +275,18 @@ def update_points(self):
 
         self.end_effector = np.array(self.points[self.n_links]).T
 
-    def plot_arm(self, myplt, obstacles=[]):  # pragma: no cover
+    def plot_arm(self, myplt, obstacles=None):  # pragma: no cover
         myplt.cla()
+        if obstacles is None:
+            obstacles = []
 
         for obstacle in obstacles:
             circle = myplt.Circle(
                 (obstacle[0], obstacle[1]), radius=0.5 * obstacle[2], fc='k')
             myplt.gca().add_patch(circle)
 
         for i in range(self.n_links + 1):
-            if i is not self.n_links:
+            if i != self.n_links:
                 myplt.plot([self.points[i][0], self.points[i + 1][0]],
                            [self.points[i][1], self.points[i + 1][1]], 'r-')
             myplt.plot(self.points[i][0], self.points[i][1], 'k.')

ArmNavigation/n_joint_arm_to_point_control/NLinkArm.py

@@ -56,7 +56,7 @@ def plot(self):  # pragma: no cover
                 lambda event: [exit(0) if event.key == 'escape' else None])
 
         for i in range(self.n_links + 1):
-            if i is not self.n_links:
+            if i != self.n_links:
                 plt.plot([self.points[i][0], self.points[i + 1][0]],
                          [self.points[i][1], self.points[i + 1][1]], 'r-')
             plt.plot(self.points[i][0], self.points[i][1], 'ko')

ArmNavigation/n_joint_arm_to_point_control/n_joint_arm_to_point_control.py

@@ -44,7 +44,7 @@ def main():  # pragma: no cover
         errors, distance = distance_to_goal(end_effector, goal_pos)
 
         # State machine to allow changing of goal before current goal has been reached
-        if state is WAIT_FOR_NEW_GOAL:
+        if state == WAIT_FOR_NEW_GOAL:
             if distance > 0.1 and not solution_found:
                 joint_goal_angles, solution_found = inverse_kinematics(
                     link_lengths, joint_angles, goal_pos)
@@ -54,7 +54,7 @@ def main():  # pragma: no cover
                     arm.goal = end_effector
                 elif solution_found:
                     state = MOVING_TO_GOAL
-        elif state is MOVING_TO_GOAL:
+        elif state == MOVING_TO_GOAL:
             if distance > 0.1 and all(old_goal == goal_pos):
                 joint_angles = joint_angles + Kp * \
                     ang_diff(joint_goal_angles, joint_angles) * dt
@@ -103,7 +103,7 @@ def animation():
         errors, distance = distance_to_goal(end_effector, goal_pos)
 
         # State machine to allow changing of goal before current goal has been reached
-        if state is WAIT_FOR_NEW_GOAL:
+        if state == WAIT_FOR_NEW_GOAL:
 
             if distance > 0.1 and not solution_found:
                 joint_goal_angles, solution_found = inverse_kinematics(
@@ -114,7 +114,7 @@ def animation():
                     arm.goal = get_random_goal()
                 elif solution_found:
                     state = MOVING_TO_GOAL
-        elif state is MOVING_TO_GOAL:
+        elif state == MOVING_TO_GOAL:
             if distance > 0.1 and all(old_goal == goal_pos):
                 joint_angles = joint_angles + Kp * \
                     ang_diff(joint_goal_angles, joint_angles) * dt

Mapping/grid_map_lib/grid_map_lib.py

@@ -152,7 +152,7 @@ def set_value_from_polygon(self, pol_x, pol_y, val, inside=True):
 
                 flag = self.check_inside_polygon(x_pos, y_pos, pol_x, pol_y)
 
-                if flag is inside:
+                if flag == inside:
                     self.set_value_from_xy_index(x_ind, y_ind, val)
 
     def calc_grid_index_from_xy_index(self, x_ind, y_ind):

PathPlanning/ProbabilisticRoadMap/probabilistic_road_map.py

@@ -205,7 +205,7 @@ def dijkstra_planning(sx, sy, gx, gy, road_map, sample_x, sample_y):
             else:
                 open_set[n_id] = node
 
-    if path_found is False:
+    if not path_found:
         return [], []
 
     # generate final course

PathPlanning/TimeBasedPathPlanning/GridWithDynamicObstacles.py

@@ -35,9 +35,9 @@ class Grid:
     # Set in constructor
     grid_size: np.ndarray
     reservation_matrix: np.ndarray
-    obstacle_paths: list[list[Position]] = []
+    obstacle_paths: list[list[Position]]
     # Obstacles will never occupy these points. Useful to avoid impossible scenarios
-    obstacle_avoid_points: list[Position] = []
+    obstacle_avoid_points: list[Position]
 
     # Number of time steps in the simulation
     time_limit: int
@@ -49,15 +49,18 @@ def __init__(
         self,
         grid_size: np.ndarray,
         num_obstacles: int = 40,
-        obstacle_avoid_points: list[Position] = [],
+        obstacle_avoid_points: list[Position] | None = None,
         obstacle_arrangement: ObstacleArrangement = ObstacleArrangement.RANDOM,
         time_limit: int = 100,
     ):
+        if obstacle_avoid_points is None:
+            obstacle_avoid_points = []
         self.obstacle_avoid_points = obstacle_avoid_points
         self.time_limit = time_limit
         self.grid_size = grid_size
         self.reservation_matrix = np.zeros((grid_size[0], grid_size[1], self.time_limit))
 
+        self.obstacle_paths = []
         if num_obstacles > self.grid_size[0] * self.grid_size[1]:
             raise Exception("Number of obstacles is greater than grid size!")