Python Cookbook
This section contains a list of recipes that complement the [tutorial](../python_api_tutorial/) and are used to
illustrate the use of Python API methods.
Each recipe has a list of [python API classes](../python_api/), which is divided into those in which the recipe is centered,
and those that need to be used.
There are more recipes to come!
## Actor Spectator Recipe
This recipe spawns an actor and the spectator camera at the actor's location.
Focused on:
[`carla.World`](../python_api/#carla.World)
[`carla.Actor`](../python_api/#carla.Actor)
Used:
[`carla.WorldSnapshot`](../python_api/#carla.WorldSnapshot)
[`carla.ActorSnapshot`](../python_api/#carla.ActorSnapshot)
```py
# ...
world = client.get_world()
spectator = world.get_spectator()
vehicle_bp = random.choice(world.get_blueprint_library().filter('vehicle.bmw.*'))
transform = random.choice(world.get_map().get_spawn_points())
vehicle = world.try_spawn_actor(vehicle_bp, transform)
# Wait for world to get the vehicle actor
world.tick()
world_snapshot = world.wait_for_tick()
actor_snapshot = world_snapshot.find(vehicle.id)
# Set spectator at given transform (vehicle transform)
spectator.set_transform(actor_snapshot.get_transform())
# ...
```
## Attach Sensors Recipe
This recipe attaches different camera / sensors to a vehicle with different attachments.
Focused on:
[`carla.Sensor`](../python_api/#carla.Sensor)
[`carla.AttachmentType`](../python_api/#carla.AttachmentType)
Used:
[`carla.World`](../python_api/#carla.World)
```py
# ...
camera = world.spawn_actor(rgb_camera_bp, transform, attach_to=vehicle, attachment_type=Attachment.SpringArm)
# Default attachment: Attachment.Rigid
gnss_sensor = world.spawn_actor(sensor_gnss_bp, transform, attach_to=vehicle)
collision_sensor = world.spawn_actor(sensor_collision_bp, transform, attach_to=vehicle)
lane_invasion_sensor = world.spawn_actor(sensor_lane_invasion_bp, transform, attach_to=vehicle)
# ...
```
## Actor Attribute Recipe
This recipe changes attributes of different type of blueprint actors.
Focused on:
[`carla.ActorAttribute`](../python_api/#carla.ActorAttribute)
[`carla.ActorBlueprint`](../python_api/#carla.ActorBlueprint)
Used:
[`carla.World`](../python_api/#carla.World)
[`carla.BlueprintLibrary`](../python_api/#carla.BlueprintLibrary)
```py
# ...
walker_bp = world.get_blueprint_library().filter('walker.pedestrian.0002')
walker_bp.set_attribute('is_invincible', True)
# ...
# Changes attribute randomly by the recommended value
vehicle_bp = wolrd.get_blueprint_library().filter('vehicle.bmw.*')
color = random.choice(vehicle_bp.get_attribute('color').recommended_values)
vehicle_bp.set_attribute('color', color)
# ...
camera_bp = world.get_blueprint_library().filter('sensor.camera.rgb')
camera_bp.set_attribute('image_size_x', 600)
camera_bp.set_attribute('image_size_y', 600)
# ...
```
## Converted Image Recipe
This recipe applies a color conversion to the image taken by a camera sensor, so it is converted to a
semantic segmentation image.
Focused on:
[`carla.ColorConverter`](../python_api/#carla.ColorConverter)
[`carla.Sensor`](../python_api/#carla.Sensor)
```py
# ...
camera_bp = world.get_blueprint_library().filter('sensor.camera.semantic_segmentation')
# ...
cc = carla.ColorConverter.CityScapesPalette
camera.listen(lambda image: image.save_to_disk('output/%06d.png' % image.frame, cc))
# ...
```
## Lanes Recipe
This recipe shows the current traffic rules affecting the vehicle. Shows the current lane type and
if a lane change can be done in the actual lane or the surrounding ones.
Focused on:
[`carla.LaneMarking`](../python_api/#carla.LaneMarking)
[`carla.LaneMarkingType`](../python_api/#carla.LaneMarkingType)
[`carla.LaneChange`](../python_api/#carla.LaneChange)
[`carla.LaneType`](../python_api/#carla.LaneType)
Used:
[`carla.Waypoint`](../python_api/#carla.Waypoint)
[`carla.World`](../python_api/#carla.World)
```py
# ...
waypoint = world.get_map().get_waypoint(vehicle.get_location(),project_to_road=True, lane_type=(carla.LaneType.Driving | carla.LaneType.Shoulder | carla.LaneType.Sidewalk))
print("Current lane type: " + str(waypoint.lane_type))
# Check current lane change allowed
print("Current Lane change: " + str(waypoint.lane_change))
# Left and Right lane markings
print("L lane marking type: " + str(waypoint.left_lane_marking.type))
print("L lane marking change: " + str(waypoint.left_lane_marking.lane_change))
print("R lane marking type: " + str(waypoint.right_lane_marking.type))
print("R lane marking change: " + str(waypoint.right_lane_marking.lane_change))
# ...
```
## Debug Bounding Box Recipe
This recipe shows how to draw traffic light actor bounding boxes from a world snapshot.
Focused on:
[`carla.DebugHelper`](../python_api/#carla.DebugHelper)
[`carla.BoundingBox`](../python_api/#carla.BoundingBox)
Used:
[`carla.ActorSnapshot`](../python_api/#carla.ActorSnapshot)
[`carla.Actor`](../python_api/#carla.Actor)
[`carla.Vector3D`](../python_api/#carla.Vector3D)
[`carla.Color`](../python_api/#carla.Color)
```py
# ....
debug = world.debug
world_snapshot = world.get_snapshot()
for actor_snapshot in world_snapshot:
actual_actor = world.get_actor(actor_snapshot.id)
if actual_actor.type_id == 'traffic.traffic_light':
debug.draw_box(carla.BoundingBox(actor_snapshot.get_transform().location,carla.Vector3D(0.5,0.5,2)),actor_snapshot.get_transform().rotation, 0.05, carla.Color(255,0,0,0),0)
# ...
```
## Traffic lights Recipe
This recipe changes from red to green the traffic light that affects the vehicle.
This is done by detecting if the vehicle actor is at a traffic light.
Focused on:
[`carla.TrafficLight`](../python_api/#carla.TrafficLight)
[`carla.TrafficLightState`](../python_api/#carla.TrafficLightState)
Used:
[`carla.Vehicle`](../python_api/#carla.Vehicle)
```py
# ...
if vehicle_actor.is_at_traffic_light():
traffic_light = vehicle_actor.get_traffic_light()
if traffic_light.get_state() == carla.TrafficLightState.Red:
# world.hud.notification("Traffic light changed! Good to go!")
traffic_light.set_state(carla.TrafficLightState.Green)
# ...
```
