ImportError: dynamic module does not define module export function (PyInit_bindings)

[skavrx]

Hi, I've been trying to install the actuator package onto my Jetson Nano. It is an older one, running JetPack 4.6 on Ubuntu 18.04 Bionic.

Jtop Output:

I setup a python virtual env with python 3.11 and used pip to install the actuator from pypip. Got this error. I also tried installing from the github source, got the same error.

(bike-env) ltr@defoliation-droid:~/Desktop$ python test_robstride.py 
Traceback (most recent call last):
  File "/home/ltr/Desktop/test_robstride.py", line 5, in <module>
    from actuator import RobstrideMotorsSupervisor
  File "/home/ltr/Desktop/bike-env/lib/python3.11/site-packages/actuator/__init__.py", line 3, in <module>
    from .bindings import (
ImportError: dynamic module does not define module export function (PyInit_bindings)

I am just trying to run the test code from the current docs:

import argparse
import math
import time
 
from actuator import RobstrideMotorsSupervisor
 
# Parse command line arguments.
parser = argparse.ArgumentParser()
parser.add_argument("--port-name", type=str, default="/dev/ttyUSB0")
parser.add_argument("--motor-id", type=int, default=1)
parser.add_argument("--motor-type", type=str, default="01")
parser.add_argument("--sleep", type=float, default=0.0)
parser.add_argument("--period", type=float, default=10.0)
parser.add_argument("--amplitude", type=float, default=1.0)
parser.add_argument("--verbose", action="store_true")
args = parser.parse_args()
 
amplitude = args.amplitude
period = args.period
 
# This creates a motor supervisor, which sends commands to all the actuators on
# the same CAN bus at a regular interval.
supervisor = RobstrideMotorsSupervisor(args.port_name, {args.motor_id: args.motor_type})
 
# This is used to set the KP and KD parameters for the MIT Cheetah-style
# PD controller.
supervisor.set_kp(args.motor_id, 10.0)
supervisor.set_kd(args.motor_id, 1.0)
 
start_time = time.time()
 
try:
    while True:
        elapsed_time = time.time() - start_time
        target_position = amplitude * math.sin(elapsed_time * 2 * math.pi / period)
        target_velocity = amplitude * 2 * math.pi / period * math.cos(elapsed_time * 2 * math.pi / period)
        supervisor.set_position(args.motor_id, target_position)
        supervisor.set_velocity(args.motor_id, target_velocity)
        time.sleep(args.sleep)
        if args.verbose:
            feedback = supervisor.get_latest_feedback()
            print(feedback)
 
except KeyboardInterrupt:
    supervisor.stop()
    time.sleep(0.1)
    raise

[WT-MM]

Oh - we recently made a bunch of changes that haven't been updated in the docs yet. Let me verify that the Python bindings work but until then, could you try this test script instead?

# Example of reading a motor using the supervisor.

import argparse
import time

from actuator import RobstrideActuatorConfig, RobstrideSupervisor


def main() -> None:
    parser = argparse.ArgumentParser()
    parser.add_argument("--port-name", type=str, default="/dev/ttyCH341USB0")
    parser.add_argument("--motor-id", type=int, default=1)
    parser.add_argument("--motor-type", type=str, default="04")
    parser.add_argument("--sleep", type=float, default=0.0)
    parser.add_argument("--period", type=float, default=10.0)
    parser.add_argument("--amplitude", type=float, default=1.0)
    parser.add_argument("--verbose", action="store_true")
    args = parser.parse_args()

    _amplitude = args.amplitude
    _period = args.period

    supervisor = RobstrideSupervisor(
        ports=[args.port_name],
        py_actuators_config=[(args.motor_id, RobstrideActuatorConfig(args.motor_type))],
        polling_interval=args.sleep,
    )

    while True:
        print(supervisor.get_actuators_state([args.motor_id]))
        time.sleep(1)


if __name__ == "__main__":
    # python -m examples.supervisor
    main()

[skavrx]

Still getting the same error with that script

(bike-env) ltr@defoliation-droid:~/Desktop$ python test.py
Traceback (most recent call last):
  File "/home/ltr/Desktop/test.py", line 6, in <module>
    from actuator import RobstrideActuatorConfig, RobstrideSupervisor
  File "/home/ltr/Desktop/bike-env/lib/python3.11/site-packages/actuator/__init__.py", line 3, in <module>
    from .bindings import (
ImportError: dynamic module does not define module export function (PyInit_bindings)

[WT-MM]

Can you try replacing RobstrideSupervisor with RobstrideActuator everywhere?

Actually there are some build problems - i'll get back to you in a bit

[skavrx]

I have tried replacing it with RobstrideActuator everywhere I could think of, and I tried some older code I had working. The same code works fine on Windows machine with WSL, but fails on the Jetson Nano.

[WT-MM]

Sorry, the python bindings for this have been a lot more work than I expected. If you check the linked pr, I've got an example script that reads the motors but sending commands isn't fully working yet. I expect it'll take another few days so until then, you could also look at the source Rust code or even kos to run motors.

Also super weird that it works with WSL. Not sure why that'd be the case but I've been testing this code on a Jetson AGX