diff --git a/flatland/envs/distance_map.py b/flatland/envs/distance_map.py
index 22721407f059ff2e02d907110cb9f982aa9d599e..2bc1a5117794959cca82d2edad821cb629397f78 100644
--- a/flatland/envs/distance_map.py
+++ b/flatland/envs/distance_map.py
@@ -31,7 +31,6 @@ class DistanceMap:
         if self.reset_was_called:
             self.reset_was_called = False
 
-            nb_agents = len(self.agents)
             compute_distance_map = True
             # Don't compute the distance map if it was loaded
             if self.agents_previous_computation is None and self.distance_map is not None:
diff --git a/flatland/envs/grid4_generators_utils.py b/flatland/envs/grid4_generators_utils.py
index 0b866e3348728814efc721fc13a15544bde0878d..04903d3ad02ec41e9615c2bb488f24c01e163a1d 100644
--- a/flatland/envs/grid4_generators_utils.py
+++ b/flatland/envs/grid4_generators_utils.py
@@ -19,7 +19,8 @@ def connect_rail_in_grid_map(grid_map: GridTransitionMap, start: IntVector2D, en
                              rail_trans: RailEnvTransitions,
                              a_star_distance_function: IntVector2DDistance = Vec2d.get_manhattan_distance,
                              flip_start_node_trans: bool = False, flip_end_node_trans: bool = False,
-                             respect_transition_validity: bool = True, forbidden_cells: IntVector2DArray = None) -> IntVector2DArray:
+                             respect_transition_validity: bool = True,
+                             forbidden_cells: IntVector2DArray = None) -> IntVector2DArray:
     """
         Creates a new path [start,end] in `grid_map.grid`, based on rail_trans, and
     returns the path created as a list of positions.
@@ -109,7 +110,7 @@ def connect_straight_line_in_grid_map(grid_map: GridTransitionMap, start: IntVec
         length = np.abs(end[0] - start[0]) + 1
         cols = np.repeat(start[1], length)
 
-    else:   # Grid4TransitionsEnum.EAST or Grid4TransitionsEnum.WEST
+    else:  # Grid4TransitionsEnum.EAST or Grid4TransitionsEnum.WEST
         start_col = min(start[1], end[1])
         end_col = max(start[1], end[1]) + 1
         cols = np.arange(start_col, end_col)
diff --git a/flatland/envs/observations.py b/flatland/envs/observations.py
index caa3329a3b977b290443c065dcc0ac73c1014a16..8cf4d8751480558cd4bc02f42611f94f10263305 100644
--- a/flatland/envs/observations.py
+++ b/flatland/envs/observations.py
@@ -67,7 +67,7 @@ class TreeObsForRailEnv(ObservationBuilder):
             self.predicted_dir = {}
             self.predictions = self.predictor.get()
             if self.predictions:
-                for t in range(self.predictor.max_depth+1):
+                for t in range(self.predictor.max_depth + 1):
                     pos_list = []
                     dir_list = []
                     for a in handles:
@@ -162,7 +162,6 @@ class TreeObsForRailEnv(ObservationBuilder):
         In case the target node is reached, the values are [0, 0, 0, 0, 0].
         """
 
-
         # Update local lookup table for all agents' positions
         # ignore other agents not in the grid (only status active and done)
         self.location_has_agent = {tuple(agent.position): 1 for agent in self.env.agents if