[Python-Dev] Documentation about Python's GC, python-dev list messages referenced in Modules/gcmodule.c not reachable anymore

[Josiah Carlson]

Tim Peters <tim.peters at gmail.com> wrote:
> 
> [Josiah Carlson]
> > I believe this particular argument is specious.
> 
> Not at all, but it's not compelling on its own.

I like that better.

> > Using Python won't change requirements for knowing what is or is
> > not referenced during program execution for "real time" development.
> >  Further, "real time" developers won't be using arbitrary 3rd party code
> > which may do unknown crazy things, it'll all be known crazy things.
> 
> So you believe they're not going to use any code they didn't write
> from scratch themselves?

Of course not.

> For example, they're not going to use the
> Python libraries?  Not going to use core Python data types?  "3rd
> party" seems a wrong distinction if "wholly understood" is what's
> relevant.  Even something as simple as list.append(3) _can_ cause a
> long delay, and that's not a "_known_ crazy thing" unless you're an
> expert in Python internals.

If someone is planning on using Python for real time systems, and they
don't know that Python uses arrays as lists, then they aren't paying
attention to the stuff they should be - exactly those Python internals
that _can_ affect their running time.  Considering that Mr. Weber was
asking about the Python garbage collector specifically, I would imagine
that they have at least started delving into the inner workings of
Python data structures.

I personally don't build real-time systems, but if I did, the first
thing I would do is remove everything from the standard library.  As the
code in the standard library is verified, validated, and its running
time documented (as such module functionality is requested), I'd add
them into the standard library.  The first things that I would document
would be all of the objects which sit in __builtins__ .  But who knows,
maybe real-time people aren't as anal about correctness as a CS Theory
grad student - though I would guess they are a bit more anal than I am
(what with all that formal correctness and proof training that some of
my eastern European friends poke me in the ribs about).


> > My flight-controller-software-validator friend tells me that they use a
> > slimmed-down variant of Python for some of their software, and that it
> > works great.
> 
> Then I hope that and a marketing department makes you rich ;-)

I'm completely detached from his work and what he does, and he's a
salaried employee.  Only the guys on the top are getting rich.

 - Josiah