rtspbuffercam can be used to connect to and read images for rtsp enabled camera's.
It uses sub processes to exhaust camera's buffer and eliminate any lag that might occur using a vanilla opencv connection.
Using pypi
pip install rtspbuffercam
or from source
git clone https://github.com/lewis-morris/rtspbuffercam
cd rtspbuffercam
python setup.py install
#import the rtspcam
from rtspcam import Camera
#create a new rtspcam object
cam = Camera("rtsp://admin:[your password]@192.168.0.40/h264Preview_01_main")
#read image
image = cam.get_frame()