How to Fix The Leap Motion Error Device in Python

When I first started working with Leap Motion using Python, I was really excited to build a simple application that could detect hand gestures and fingers. However, I quickly ran into an error that stopped me in my tracks. I want to share my experience with you: the original code I wrote, the error I encountered, how I fixed it, and how I improved my project with some added functionality.

My Leap Motion Python Application Code

Here’s the initial code I wrote for my Leap Motion listener in Python:

Leap, sys, thread, time
from Leap import CircleGesture, KeyTapGesture, ScreenTapGesture, SwipeGesture, Listener


class LeapMotionListener(Leap, Listener):
    finger_name = ['a', 'b', 'c', 'd', 'e']
    bone_name = ['a1', 'b1', 'c1', 'd1']
    state_name = ['s1', 's2', 's3', 's4']

    def on_init(self, controller):
        print('initialized')

    def on_connect(self, controller):
        print('connected')
        controller.enable_gesture(Leap.Gesture.TYPE_CIRCLE)
        controller.enable_gesture(Leap.Gesture.TYPE_KEY_TAP)
        controller.enable_gesture(Leap.Gesture.TYPE_SCREEN_TAP)
        controller.enable_gesture(Leap.Gesture.TYPE_SWIPE)

    def on_disconnect(self, controller):
        print('disconnected')

    def on_exit(self, controller):
        print('Exited')

    def on_frame(self, controller):
        pass

    def main(self):
        listener = LeapMotionListener()
        controller = Leap.Controller()
        controller.add_listener(listener)

        print('press enter to quit')
        try:
            sys.stdin.readline()
        except KeyboardInterrupt:
            pass
        finally:
            controller.remove_listener(listener)


if __name__ == "__main__":
    LeapMotionListener.main()

This was my first attempt to get Leap Motion working with Python. However, when I ran this code, I immediately got the following error:

: DLL load failed: %1 is not a valid Win32 application.

Define the Error

This error was confusing at first, but after some research, I learned that it typically means Python is trying to load a DLL file (a dynamic link library) that doesn’t match the environment. The most common reasons are:

• Architecture mismatch: For example, running 64-bit Python but trying to load 32-bit Leap Motion DLLs (or the other way around).
• Incorrect Leap Motion SDK installation or missing dependencies.
• A naming conflict: I had a file called Leap.py in my project folder, which caused Python to import my file instead of the official Leap Motion SDK.
• Using the wrong Python version: The Leap Motion SDK works best with specific Python versions, usually Python 2.7 or certain 3.x versions.
• Missing Visual C++ Redistributables: These are sometimes required by the DLLs.

I also discovered that installing win32api did not fix this issue because it’s unrelated.

How I Fixed It

Here’s what helped me solve the problem:

1. Check Python and SDK architecture
   I made sure my Python version and the Leap Motion SDK DLLs were both 64-bit (or both 32-bit). Mixing them will always cause this error.
2. Rename your script files
   I renamed my Leap.py file to something else like leap_app.py to avoid shadowing the official Leap SDK module.
3. Reinstall the Leap Motion SDK
   I carefully followed the official installation steps, ensuring the Python bindings were installed properly.
4. Verify the Python version compatibility
   I used Python 2.7 as recommended by the Leap Motion SDK docs.
5. Install required dependencies
   I installed the Visual C++ Redistributables from Microsoft’s website to cover any missing system libraries.

Fix My Code Structure

After fixing the environment and the import error, I also realized my code had some design issues:

• I was inheriting from both Leap (a module) and Listener, but I should only inherit from Leap.Listener.
• My main() method was an instance method but called as a static method, which doesn’t work well.
• The thread module is outdated; I should use threading if needed.
• The on_frame method was empty; I wanted it to do something useful.

Improved Leap Motion Listener Code

Here’s the improved and working version of my Leap Motion listener with added gesture detection functionality:

sys
import Leap
from Leap import CircleGesture, KeyTapGesture, ScreenTapGesture, SwipeGesture, Listener


class LeapMotionListener(Listener):

    def on_init(self, controller):
        print("Initialized")

    def on_connect(self, controller):
        print("Connected")
        controller.enable_gesture(Leap.Gesture.TYPE_CIRCLE)
        controller.enable_gesture(Leap.Gesture.TYPE_KEY_TAP)
        controller.enable_gesture(Leap.Gesture.TYPE_SCREEN_TAP)
        controller.enable_gesture(Leap.Gesture.TYPE_SWIPE)

    def on_disconnect(self, controller):
        print("Disconnected")

    def on_exit(self, controller):
        print("Exited")

    def on_frame(self, controller):
        frame = controller.frame()
        hands = frame.hands
        if not hands.is_empty:
            for hand in hands:
                hand_type = "Left hand" if hand.is_left else "Right hand"
                fingers = hand.fingers
                print(f"{hand_type} detected with {fingers.count} fingers.")
                
                # Detect circle gestures and print details
                for gesture in frame.gestures():
                    if gesture.type == Leap.Gesture.TYPE_CIRCLE:
                        circle = CircleGesture(gesture)
                        print(f"Circle gesture detected: Radius = {circle.radius:.2f}")


def main():
    listener = LeapMotionListener()
    controller = Leap.Controller()
    controller.add_listener(listener)

    print("Press Enter to quit...")
    try:
        sys.stdin.readline()
    except KeyboardInterrupt:
        pass
    finally:
        controller.remove_listener(listener)


if __name__ == "__main__":
    main()

Additional Ideas for Practice and Improvement

Once this worked, I experimented with adding:

• More gesture types: Detecting swipe, key tap, and screen tap gestures.
• Hand and finger tracking: Printing positions or directions of individual fingers.
• Logging data: Writing detected gestures and hand info to a file for analysis.
• Interactive commands: Triggering different print statements or app modes based on gestures, like swiping left or right.

These made the project more interactive and helped me understand the Leap Motion API better.

Final Thought

Working with Leap Motion and Python was an exciting learning journey. The tricky DLL import error taught me the importance of matching architectures and avoiding module shadowing. Cleaning up my code and adding meaningful gesture detection made the app practical and enjoyable.

If you’re starting with Leap Motion and Python, I encourage you to check your environment carefully, follow SDK instructions closely, and build your project incrementally. Small steps with constant testing will save you from many common pitfalls.