[Python-Dev] Can someone look at dummy_thread (#622537)?

[Brett Cannon]

[Guido van Rossum]

> > > >     try:
> > > >         import threading
> > > >     except ImportError:
> > > >         threading = None # use non-threaded behaviour
> > >
> > > But then you'd have to sprinkle the rest of the code with
> > > "if threading is not None" tests.  Brett's dummy_thread is an attempt
> > > to reduce this clutter.
> >
> > the problem (if there is one) is that the proposed integration may
> > break code that uses the above pattern.
>

But if it does it will be on platforms it couldn't run on previously.
``threading`` uses ``thread`` when possible and only falls back on
``dummy_thread`` when it isn't available.  That means this could only be a
problem where  the code  was not even runnable before.

But yes, there are chances of deadlock in certain situations.  It
basically comes down to whether we want to protect users from themselves
by not having them get into a possible deadlock situation.

> I don't propose to automate this.  I propose this:
>
>   try:
>     import threading
>   except ImportError:
>     import dummy_threading as threading
>

So is this an indirect request for me to write ``dumy_threading``?  If it
is it won't be hard: I would do an ``import *`` on ``threading`` and then
override the functions it uses from ``thread`` with ``import ... from ...
as ...`` from ``dummy_thread``.  Also would mean rewriting the
``threading`` testing suite.  Prefectly happy to write it, just need you
to say you want it.

-Brett