On 6/10/2020 8:33 AM, Mark Shannon wrote:
Hi Petr,
On 09/06/2020 2:24 pm, Petr Viktorin wrote:
On 2020-06-05 16:32, Mark Shannon wrote:
Whether Python interpreters run sequentially or in parallel, having
them work will enable a use case I would like to see: allowing me to
call Python code from wherever I want, without thinking about global
state. Think calling Python from an utility library that doesn't care
about the rest of the application it's used in. I personally call
this "the Lua use case", because light-weight, worry-free embedding
is an area where Python loses to Lua. (And JS as well—that's a
relatively recent development, but much more worrying.)
This seems like a worthwhile goal. However I don't see why this
requires having multiple Python interpreters in a single O/S process.
I assume it would be so that my code could link with library A, which
embeds Python, and library B, which also embeds Python. A and B have no
knowledge of each other.
The part I have been involved in is moving away from process-global
state. Process-global state can be made to work, but it is much safer
to always default to module-local state (roughly what
Python-language's `global` means), and treat process-global state as
exceptions one has to think through. The API introduced in PEPs 384,
489, 573 (and future planned ones) aims to make module-local state
possible to use, then later easy to use, and the natural default.
I don't agree. Process level state is *much* safer than module-local
state.
Suppose two interpreters, have both imported the same module.
By using O/S processes to keep the interpreters separate, the hardware
prevents the two copies of the module from interfering with each other.
By sharing an address space the separation is maintained by trust and
hoping that third party modules don't have too many bugs.
I don't see how you can claim the later case if safer.
I've always assumed that per-module state meant per-module,
per-interpreter. Maybe I've misunderstood, in which case I agree with
Mark. If per-module state isn't isolated per interpreter, that sort of
kills the multiple interpreter model, in my mind.
Eric
_______________________________________________
Python-Dev mailing list -- python-dev@python.org
To unsubscribe send an email to python-dev-le...@python.org
https://mail.python.org/mailman3/lists/python-dev.python.org/
Message archived at
https://mail.python.org/archives/list/python-dev@python.org/message/WOOPV4QKFFZSZ5QVXMC3JBEHPTVULH4S/
Code of Conduct: http://python.org/psf/codeofconduct/
