Re: Callback error from pyepics and python with GUI development

[Tong Zhang via Tech-talk <tech-talk@aps.anl.gov>]

Hi Matt,

Just tried this PR (https://github.com/pyepics/pyepics/pull/150), it 
solved my issue (probably threading race condition), thank Daron for the 
help!

Hope you'll merge this PR soon.

Tong


On 4/11/19 6:52 PM, Tong Zhang via Tech-talk wrote:
> Hi Matt,
>
> I think the following issue I encountered may have something to do with 
> pyepics, which after discussing with Daron, still cannot be resolved yet.
>
> I'm trying to create pv callbacks onto my high-level GUI application 
> with pyepics, but the app crashed because of the error regarding the CA 
> context, please see the attached screenshot. And the strange thing is 
> this only happened to Python 3.5, not Python 3.6 and Python 3.7.
>
> To my understanding, the GUI case is slightly different than python 
> thread, the main thread is for UI rendering, all my created callback are 
> spawned from this main thread, I can do other CA action (put/get) 
> without any problem, so where is the default CA context in the GUI case?
>
> I've checked this link 
> https://github.com/pyepics/pyepics/issues/68#issuecomment-290892241 and 
> the guideline for python thread with pyepics, but still not sure how can 
> I make use of the context.
>
> Appreciate for any reply,
> Tong