在python中选择cv2中的usb摄像头

import cv2

def get_available_cameras():
    camera_list = []
    index = 0
    while True:
        cap = cv2.VideoCapture(index)
        if not cap.read()[0]:
            break
        else:
            camera_list.append(index)
        cap.release()
        index += 1
    return camera_list

def open_camera(camera_index):
    cap = cv2.VideoCapture(camera_index)
    if not cap.isOpened():
        print("Failed to open camera!")
        return
    while True:
        ret, frame = cap.read()
        if not ret:
            print("Failed to capture frame!")
            break
        cv2.imshow("Camera", frame)
        if cv2.waitKey(1) & 0xFF == ord('q'):
            break
    cap.release()
    cv2.destroyAllWindows()

available_cameras = get_available_cameras()
if len(available_cameras) > 0:
    camera_index = available_cameras[0]  # 选择第一个可用摄像头
    open_camera(camera_index)
else:
    print("No available cameras found!")