How do I add a mobile geolocation marker into a Folium webmap that automatically updates position?
OK, I have figured out a main part of the question - how to add a user location marker to the Folium map.  It is actually very simple:
https://python-visualization.github.io/folium/plugins.html#folium.plugins.LocateControl
I am still unable to pass the user's lat/lon through to my python script so that I can perform spatial queries using that location.  So am looking forward to anyone being able to answer that part.  Though I may have to post that as a separate question perhaps...
I have a webmap which is made in python using Folium.  I am adding various geojson layers from an underlying database.  I would like to do spatial analysis based on the user's location and their position relative to the various map overlays.  As part of this I want to display a marker on the map which indicates the user's current position, and which updates regularly as they move around.
I know how to add markers to the map from within python, using Folium.
I know how to get a constantly updating latitude / longitude of the user using JS 
navigator.geolocation.watchPosition(showPosition)
which then passes a position variable to the function showPosition.
I am currently just displaying this as text on the website for now.
What I have not been able to do is to add a marker to the Folium map from inside the webpage, using JS/Leaflet (as Folium is just a wrapper for Leaflet, i think I should be able to do this).  
The Folium map object seems to be assigned a new variable name every time the webpage is loaded, and I don't know how to "get" the map element and add a marker using the Leaflet syntax 
L.marker([lat, lon]).addTo(name_of_map_variable_which_keeps_changing)
Alternatively there might be a way to "send" the constantly changing lat/lon variables from the webpage back to the python script so that I can just use folium to add the marker.  
But I have been unable to figure this out or find the right assistance online and would appreciate any help.