Problem with using opencv in python

[Pedroski55]

Oh dear! What os are you using?

I use Ubuntu 22.04, I am doing this in Idle.

def camON():
    print('This is function camON() starting ... ')
    cap = cv2.VideoCapture(0)
    if not cap.isOpened():
        print("Error: Could not open camera.")     
        return   
    else:
        while True:
            ret, frame = cap.read()
            if not ret:
                print("Error: Could not read frame.")
                break
            cv2.imshow('Camera Feed', frame)
            # setting waitKey(0) freezes the picture while you wait
            # cv2.waitKey(1) waits 1 millisecond so the picture stays alive
            key = cv2.waitKey(1)
            if key == 27 or key == 113: # esc or q to quit
                break                                
    cap.release()
    cv2.destroyAllWindows()
    print(f'Escape key was {chr(key)}.')
    return key

The ouput, apart from the window with my ugly face, in Idle is:

Output:
camON()
This is function camON() starting ... 
Escape key was q.
113

When I changed

cap = cv2.VideoCapture(0)
to
cap = cv2.VideoCapture(1)

I get this in Idle:

Output:
camON()
This is function camON() starting ... 
Error: Could not open camera.
Traceback (most recent call last):
  File "/usr/lib/python3.10/idlelib/run.py", line 578, in runcode
    exec(code, self.locals)
  File "<pyshell#19>", line 1, in <module>
  File "<pyshell#18>", line 20, in camON
UnboundLocalError: local variable 'key' referenced before assignment

Could it be that you have more than 1 cam? Try a different number? Strange that you don't get any message at all.

If you run the above function camON() in Idle, do you at least see see:

This is function camON() starting ...