Since jetson nano is cpu arm64, so although the linux system, but not a lot of places and pc confused. This is in addition to supporting the use of imx219 camera (csi Interface), nor can you use cv2.VideoCapture (0) to turn on the camera, you need to use csi-camera official source. Environment configuration code and spend a little time before the results of it. 
Will upload my code, you can download the code down and discuss after me.
Configuring this environment, mainly opencv (greater than version 3.4), gstreamer, numpy, plus other will complain Failed to load module database, essentially the pip and can be installed apt, opencv most complex, but also cmake and make, about an hour. After the detection of recommendations about the installed version installed sure you have installed, or reload time, it will not only remind cover is up to date.
NOTE: If you start a program, find the camera open, suggesting gstreamer pipeline or wrong, try the following code:
sudo systemctl restart nvargus-daemon
Csi-camera and attach opencv source link, not science online.
OpenCV: HTTPS: //docs.opencv.org/3.3.1/d6/d00/tutorial_py_root.html
csi-Camera: HTTPS: //github.com/JetsonHacksNano/CSI-Camera
Summary: The fall into a pit can not save. Look at the source code, multi-search solutions abroad, repeated testing is the most effective shortcut.
