Capturing video from two cameras in OpenCV at once

Using OPENCV and two standard USB cameras, I was able to do this using multithreading. Essentially, define one function which opens an opencv window and VideoCapture element. Then, create two threads with the camera ID and window name as inputs.

import cv2
import threading

class camThread(threading.Thread):
    def __init__(self, previewName, camID):
        threading.Thread.__init__(self)
        self.previewName = previewName
        self.camID = camID
    def run(self):
        print "Starting " + self.previewName
        camPreview(self.previewName, self.camID)

def camPreview(previewName, camID):
    cv2.namedWindow(previewName)
    cam = cv2.VideoCapture(camID)
    if cam.isOpened():  # try to get the first frame
        rval, frame = cam.read()
    else:
        rval = False

    while rval:
        cv2.imshow(previewName, frame)
        rval, frame = cam.read()
        key = cv2.waitKey(20)
        if key == 27:  # exit on ESC
            break
    cv2.destroyWindow(previewName)

# Create two threads as follows
thread1 = camThread("Camera 1", 1)
thread2 = camThread("Camera 2", 2)
thread1.start()
thread2.start()

Great resource for learning how to thread in python: https://www.tutorialspoint.com/python/python_multithreading.htm