Cannot run scenario runner - "No module named 'carla'"

Hi everyone,

Im new by CARLA. I wanted to test the scenario runner, but im having some issues.

Im using CARLA from Package (9.11), so i make the download from scenario runner for the version 9.11 ( Release CARLA Scenario Runner 0.9.11 · carla-simulator/scenario_runner (

But by trying the basic example:

python --scenario FollowLeadingVehicle_1 --reloadWorld

i got this error:

Traceback (most recent call last):
File “”, line 31, in
import carla
ModuleNotFoundError: No module named ‘carla’

For information, CARLA is already “open”.

Can anyone help me?



Hi @LucasKobernic, welcome to CARLA. Have you set the environment variables like it says in this step?

Hi corkyw10,

Thanks for the tip. I set the envinronment variables and installed all python packages needed. But now, im getting this error:

Preparing scenario: FollowLeadingVehicle_1
The scenario cannot be loaded
Traceback (most recent call last):
File “”, line 389, in _load_and_run_scenario
File “C:\Users\z239023\CARLA_0.9.11\WindowsNoEditor\scenario_runner-0.9.11/srunner/scenarios\”, line 75, in init
File “C:\Users\z239023\CARLA_0.9.11\WindowsNoEditor\scenario_runner-0.9.11\srunner\scenarios\”, line 63, in init
behavior = self._create_behavior()
File “C:\Users\z239023\CARLA_0.9.11\WindowsNoEditor\scenario_runner-0.9.11/srunner/scenarios\”, line 125, in _create_behavior
AttributeError: type object ‘ParallelPolicy’ has no attribute ‘SUCCESS_ON_ONE’
type object ‘ParallelPolicy’ has no attribute ‘SUCCESS_ON_ONE’
Destroying ego vehicle 908
ERROR: failed to destroy actor 908 : unable to destroy actor: not found
No more scenarios … Exiting

Can you help me with this?

Hey @LucasKobernic. From your logs, the issue seems to be related to py_trees. ScenarioRunner has to use py_trees with version 0.8.3 so can you make sure that your version is correct?

Hi Guilherme, thanks for the information.

This was the problem ! I had a newest version from py_trees installed. After a i change to the version 0.8.3 it works!

Thanks for the help,