Utilities to make use of new "interpreters" module in Python 3.12
Status: alpha
Usage: for now one must build cpython 3.12 alpha from the main cpython branch
then, just import "extrainterpreters" and use the Interpreter class
as a wrapper to the subinterpreter represented by a single integer
handle created by the new interpreters module (that should be
in Python stdlib as soon as Eric Snow polishes it)
with an extrainterpreter.Interpreter instance, one can call:
inter.run(func_name, *args, **kwargs}) to run code there in the same
thread: the return value is just returned as long as it is pickleable.
The inter.run_in_thread with the same signature, will start a fresh
thead and call the target function there - the Interpreter instance then should
be pooled in its "done()" method, and once done, the return value
will be available by calling "result".
Also working is a threading like interface:
from extrainterpreters import Interpreter
...
interp = Interpreter(target=myfunc, args=(...,))
interp.start()
...
interp.join()
# bonus: we have return values!
print(interp.result()
It will even work for methods defined on the REPL, so, just give it a try.
There is a new class in the works which will be able to
run code in the sub-interpreter without depending of the
PEP554 "run_string" (once the setup is done). All processing in the sub-
interpreter will automatically take place in another thread,
and the roadmap is towards having a Future object and
an InterpreterPoolExecutor compatible with the
existing executors in concurrent.Futures
A lot of things here are subject to change. For now, all data exchange takes place in a custom memory buffer with 10MB (it is a bytearray on the parent interpreter, and a memoryview for that on the target)
Data is passed to and back the interpreter using pickle - so, no black magic trying to "kill an object here" and "make it be born there" (not even if I intended to, as ctypes is not currently importable on sub-interpreters).
The good news is that pickle will take care of importing whatever is
needed on the other side, so that a function can run.
I plan to get this compatible with concurrent.futures.Executor, and have an easy way to schedule a subinterpreter function execution as an async task.
Also, I should come up with a Queue object to pass data back and forth. As for the data passing mechanism: we will use pickle, no doubt.
As soon as I get to a well thought way of creating the initial buffer for comunication with a sub-interpreter.
The initial implementation used a pre-allocated mmaped file to send/get data from other interpreters, until I found out the mmap call in the sub-interpreter would build a separate mmap object in a different memory region, and a lot of data copying was taking place.
Currently, two C methods retrieve the address of an object implementing the buffer interface, and create a "stand alone" memoryview instance from the address alone. This address is passed to the subinterpreter as a string during the setup stage,