[PyQt] Any way to run code before each QThread?

[Phil Thompson]

On 15 Jul 2018, at 4:24 pm, Ned Batchelder <ned at nedbatchelder.com> wrote:
> 
> On 7/15/18 10:55 AM, Florian Bruhin wrote:
>> On Sun, Jul 15, 2018 at 04:43:41PM +0200, David Boddie wrote:
>>> On Sun Jul 15 12:30:55 BST 2018, Ned Batchelder wrote:
>>> 
>>>> I maintain coverage.py.  I have an issue
>>>> (https://github.com/nedbat/coveragepy/issues/582) that the code running
>>>> in QThreads aren't measured.  For the stdlib threading module, I have
>>>> code that runs as each thread is created to start the measurement.  Is
>>>> there any way to do the same for QThreads?
>>> Perhaps. See below.
>>> 
>>>> The stdlib feature is threading.settrace
>>>> (https://docs.python.org/3/library/threading.html#threading.settrace). I
>>>> didn't see anything similar for QThreads, or any other hook that would
>>>> give me control before the thread starts running.  Am I overlooking
>>>> something?
>>> From the threading.settrace docs:
>>> 
>>>  "Set a trace function for all threads started from the threading module.
>>>  The func will be passed to sys.settrace() for each thread, before its run()
>>>  method is called."
>>> 
>>> The QThread.started signal docs (https://doc.qt.io/qt-5/qthread.html#started)
>>> say this:
>>> 
>>>  "This signal is emitted from the associated thread when it starts executing,
>>>  before the run() function is called."
>>> 
>>> So it looks like almost exactly what you want. Connect this signal to a slot
>>> (function/method) and perform the same setup there.
>> That's only for a given QThread instance though - it'd probably work if
>> you could somehow find out about all QThread instances created in a
>> project, but I can't think of a good way to do that.
>> 
>> 
> 
> I've only poked around for ten minutes, but that's what I'm seeing also: I could get a signal from a specific thread, but only if I were alerted to its creation and could connect the signal.
> 
> Anyone have any other hacky^H^H^H^H^Hcreative ideas for how to accomplish this? :)

Should I implement QThread.settrace()?

If so can somebody clarify what thread the call to sys.settrace() should be made in? The new thread or the thread from which the new thread is created?

Phil