How to correctly check if a camera is available?

Question

I am using OpenCV to open and read from several webcams. It all works fine, but I cannot seem to find a way to know if a camera is available.

I tried this code (cam

Answer 1

Here is a "NOT working" solution to help you prevent tumbling over in this pitfall:

import cv2 as cv
import PySpin

print (cv.__version__)

# provided by Patrick Artner as solution to be working for other cameras than
#                                                  those of Point Grey (FLIR).

def testDevice(source):
   cap = cv.VideoCapture(source) 
   if cap is None or not cap.isOpened():
       print('Warning: unable to open video source: ', source)

# ... PySpin / Spinnaker (wrapper/SDK libary) ...

system   = PySpin.System.GetInstance()
cam_list = system.GetCameras()

cam = ''
cam_num = 0

for ID, cam in enumerate(cam_list):
    # Retrieve TL device nodemap
    if ID == cam_num:
        print ('Got cam')
        cam = cam

        cam.Init()

        # ... CV2 again ...

        for i in range(10):
            testDevice(i) # no printout