Cameratest.py: (does not function)

import cv2
print(cv2.__version__)
width=1280
height=720
flip=2
#camSet='nvarguscamerasrc sensor-id=0 ! video/x-raw(memory:NVMM), width=1280, height=720, framerate=30/1,format=NV12 ! nvvidconv flip-method='+str(flip)+' ! video/x-raw, width='+str(width)+', height='+str(height)+', format=BGRx ! videoconvert ! video/x-raw, format=BGR ! appsink'
camSet='v4l2src device=/dev/video0  ! video/x-raw, width=1280, height=720, framerate=30/1,format=YUYV442 ! nvvidconv flip-method='+str(flip)+' ! video/x-raw, width='+str(width)+', height='+str(height)+', format=BGRx ! videoconvert ! video/x-raw, format=BGR ! appsink'
#camSet ='v4l2src device=/dev/video0 ! video/x-raw,width='+str(width)+',height='+str(height)+',framerate=30/1 ! videoconvert ! appsink'
#camSet ='v4l2src device=/dev/video0 ! video/x-raw,width='+str(width)+',height='+str(height)+',framerate=30/1 ,format=YUY2 ! videoconvert ! appsink'
#camSet = 'v4l2src device =dev ! image/jpeg, width=120, height=720 ! jpegparse ! jpegdec ! video/x-raw, format=I420 !appsink max-buffers=1 drop=true'
cam=cv2.VideoCapture(camSet)
while True:
    _, frame = cam.read()
    cv2.imshow('myCam',frame)
    cv2.moveWindow('myCam',0,0)
    if cv2.waitKey(1)==ord('q'):
        break
cam.release()
cv2.destroyAllWindows()



Error code:

/home/nyp/.virtualenvs/py3cv4/bin/python /home/nyp/.virtualenvs/py3cv4/untitled/cameratest.py
4.1.2
[ WARN:0] global /home/nyp/opencv/modules/videoio/src/cap_gstreamer.cpp (711) open OpenCV | GStreamer warning: Error opening bin: could not link v4l2src0 to nvvconv0, neither element can handle caps video/x-raw, width=(int)1280, height=(int)720, framerate=(fraction)30/1, format=(string)YUYV442
[ WARN:0] global /home/nyp/opencv/modules/videoio/src/cap_gstreamer.cpp (480) isPipelinePlaying OpenCV | GStreamer warning: GStreamer: pipeline have not been created
[ERROR:0] global /home/nyp/opencv/modules/videoio/src/cap.cpp (116) open VIDEOIO(CV_IMAGES): raised OpenCV exception:

OpenCV(4.1.2) /home/nyp/opencv/modules/videoio/src/cap_images.cpp:253: error: (-5:Bad argument) CAP_IMAGES: can't find starting number (in the name of file): v4l2src device=/dev/video0  ! video/x-raw, width=1280, height=720, framerate=30/1,format=YUYV442 ! nvvidconv flip-method=2 ! video/x-raw, width=1280, height=720, format=BGRx ! videoconvert ! video/x-raw, format=BGR ! appsink in function 'icvExtractPattern'


Traceback (most recent call last):
  File "/home/nyp/.virtualenvs/py3cv4/untitled/cameratest.py", line 14, in <module>
    cv2.imshow('myCam',frame)
cv2.error: OpenCV(4.1.2) /home/nyp/opencv/modules/highgui/src/window.cpp:376: error: (-215:Assertion failed) size.width>0 && size.height>0 in function 'imshow'


Process finished with exit code 1