Here is a method using the fontTools Python library (which you can install with something like pip install fonttools ):
canonical version/location: Probably https://stackoverflow.com/questions/4458696/finding-out-what-characters-a-given-font-supports
superseded by: https://hyp.is/Z1f9kFuaEe2eHAdj5fbY2Q/stackoverflow.com/questions/4458696/finding-out-what-characters-a-given-font-supports