Multiple scripts versus single multi-threaded script

[Chris Angelico]

On Fri, Oct 4, 2013 at 4:28 AM, Roy Smith <roy at panix.com> wrote:
> Well, the GIL certainly eliminates a whole range of problems, but it's
> still possible to write code that deadlocks.  All that's really needed
> is for two threads to try to acquire the same two resources, in
> different orders.  I'm running the following code right now.  It appears
> to be doing a pretty good imitation of a deadlock.  Any similarity to
> current political events is purely intentional.

Right. Sorry, I meant that the GIL protects you from all that
happening in the lower level code (even lower than the Senate, here),
but yes, you can get deadlocks as soon as you acquire locks. That's
nothing to do with threading, you can have the same issues with
databases, file systems, or anything else that lets you lock
something. It's a LOT easier to deal with deadlocks or data corruption
that occurs in pure Python code than in C, since Python has awesome
introspection facilities... and you're guaranteed that corrupt data is
still valid Python objects.

As to your corrupt data example, though, I'd advocate a very simple
system of object ownership: as soon as the object has been put on the
queue, it's "owned" by the recipient and shouldn't be mutated by
anyone else. That kind of system generally isn't hard to maintain.

ChrisA