Developers who want to use RealSense with Python and OpenCV usually use the open-source Librealsense SDK, which apparently has pyRealSense support integrated into it.
With that SDK, some people have also used a script called cpp-tutorial-2-streams.cpp or a similar one to display 4 different types of camera stream onscreen simultaneously.
Here's a link to the cpp-tutorial-2-streams.cpp script.
This forum thread that discusses using RealSense with Python may also be of use to you.
Thank you MartyG, but I guess I need more tutorial-like instructions to install librealsense with python to get it working.
Projects on GitHub, like Librealsense, do not typically have beginner-friendly instructions, probably because they assume that people using the likes of Linux have a certain level of tech skill already. The most user-friendly installation guide for Librealsense that I could find was this one.
I also manged to dig up the link to Librealsense's own official installation guide.
Usually when presented with overly complicated manuals, I write my own setup guide instead so I know exactly how it works. Maybe I should do a beginners install guide for Librealsense some day!
As for installing Python support in Librealsense ... whilst I have not tried it myself, I notice that Librealsense's manual simply provides a link to a download for pyRealSense. This suggests to me that if you already have pyRealSense installed then Librealsense should be able to make use of it. If I'm incorrect about that, I'm sure a Librealsense / Python user in the community will kindly correct me.