[Python-ideas] install pip packages from Python prompt

Nick Coghlan ncoghlan at gmail.com
Mon Oct 30 12:22:50 EDT 2017

On 31 October 2017 at 02:06, Paul Moore <p.f.moore at gmail.com> wrote:

> On 30 October 2017 at 15:53, Antoine Pitrou <solipsis at pitrou.net> wrote:
> > On Tue, 31 Oct 2017 01:44:10 +1000
> > Nick Coghlan <ncoghlan at gmail.com> wrote:
> >> (We'd want a real process restart, rather than emulating it by calling
> >> Py_Initialize & Py_Finalize multiple times, as not every module properly
> >> supports multiple initialise/finalise cycles within a single process,
> and
> >> module-specific quirks are exactly what we'd be trying to avoid by
> forcing
> >> an interpreter restart)
> >
> > The main difference, though, is that a notebook will reload and
> > replay all your session, while restarting the regular REPL will simply
> > lose all current work.  I think that makes the idea much less
> > appealing.

Right, but if you want an installation to work reliably, you're going to
lose that state anyway. Erik's original comment included the suggestion to
"give them an opportunity to cancel the
action in case they have any work they need to save", and I think some kind
of warning's going to be necessary no matter how we handle the restart.

> Also, on Windows, I believe that any emulation of execve either leaves
> the original process in memory, or has problems getting console
> inheritance right. It's been a long time since I worked at that level,
> and things may be better now, but getting a robust "restart this
> process" interface in Windows would need some care (that's one of the
> reasons the py launcher runs Python as a subprocess rather than doing
> any sort of exec equivalent).

As long as the standard streams are passed along correctly, whatever the py
launcher does would presumably be adequate for a REPL restart as well,
assuming we decided to go down that path.

It would also be reasonable to say that the regular REPL just issues a
warning that a restart might be needed, and it's only REPLs with a separate
client process that offer a way to restart the subprocess where code
actually executes.


Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia
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