I have a Python interface of a graph library written in C - igraph (the name of library). My need is to invoke the python modules pertaining to this graph library from Java
Never tried it. But I recently stumbled on a project named Jepp that may be of interest to you.
Jepp embeds CPython in Java. It is safe to use in a heavily threaded environment, it is quite fast and its stability is a main feature and goal.