One side effect of Nick Coghlan's PEP 432 (interpreter startup) is that is makes the effort of consolidating global state (out of static variables) easier. His

One side effect of Nick Coghlan's PEP 432 (interpreter startup) is that is makes the effort of consolidating global state (out of static variables) easier. His implementation is progressing. My proposed subinterpreter-based project will likely involve the effort of pulling all remaining global interpreter state into the interpreter struct. As to supporting multiple truly independent Python interpreters in the same process, I'm not clear on what the buys you over subinterpreters. In fact, with subinterpreters you get the benefit of the main interpreter handling the C runtime global state (env vars, command line args, the standard streams, etc.). With truly independent interpreters that's more complicated. While it's not quite what you described, if you were to suggest that subinterpreters be made even more isolated from one another than they already are then I'd agree. :) It sounds like that's really what you're after: better isolation between interpreters in a single process.