Perhaps I'm missing something, but why not use QTimer? You can't really every
call sleep in a single threaded gui (for reasons you've encountered). If you
need to poll something, create a QTimer for 2 seconds and have it call a
measurement function to update the data. You shouldn't need any processEvents
calls or sleep.
________________________________________
From: Fabien Lafont [lafont.fab...@gmail.com]
Sent: Tuesday, December 13, 2011 12:30 AM
To: David Hoese
Cc: matplotlib-users@lists.sourceforge.net
Subject: Re: [Matplotlib-users] [ploting data] Live data
Hey David,
I'm doing this program to control an experiment, so I want to put the
voltage on the sample, then wait two seconds to be sure there is no
current fluctuations then measure the curent with multimeters and
finally plot the datas. That's why I need the "sleep"... In fact I
wanted to use in parallel the timer to "refresh" the graph and a while
loop to "extract" the datas.
If I use startTimer(0) it works but the GUI is almost unresponsive.
I'm trying to use qApp.processEvents() but up to now I don't manage to
see the window appears...
Thanks again for your help
Fabien
2011/12/12 David Hoese <dho...@gmail.com>:
> Hey Fabien,
>
> So you made your principal function run on a timer every 2 seconds? And by
> "lag" do you mean that the GUI is unresponsive? I'm still not seeing when
> the loop stops, but what you can do is set the timer at a 0 interval so it
> will call the principal function as fast as it can (but with no loop). The
> problem with this is that you have those 2 sleep calls in the function. I'm
> not sure why you have the sleeps, but if you need them you have two choices:
>
> 1. Make you GUI multi-threaded and you could emit a Qt signal from the data
> thread when the GUI thread needs to update the GUI. Yes this could get
> complicated, but if the sleeps are required then its probably the best way.
>
> 2. (From what I've been told, the Qt experts don't approve this) You can use
> app.processEvents() in your loop (after each sleep maybe) and this will
> pause your function and tell the main event loop to process any queued
> events (like GUI actions/events) which will make your GUI more responsive.
>
> If that doesn't make sense let me know.
>
> -Dave
>
>
> On 12/12/11 9:16 AM, Fabien Lafont wrote:
>>
>> Hi David! Sorry about the delay I was abroad and without any way to
>> connect to the internet.
>>
>> Thank you very much. I've tried to put the principal inside the
>> timerEvent. It work but it lags. In fact I've set the interval of the
>> Timer to 2 seconds because the principal loop takes roughly 2seconds
>> but it's not very accurate...
>>
>> Is there a way to do the principal loop, show it on the screen, then
>> redo the loop?
>>
>> Thanks again!
>>
>> Fabien
>>
>> 2011/12/5 David Hoese<dho...@gmail.com>:
>>>
>>> If I'm understanding your question correctly and reading your code
>>> correctly, you're asking why the timer method of doing things works, but the
>>> principal() while loop method does not.
>>>
>>> I had a couple solutions that involved the main event loop, but I just
>>> noticed 2 main things that are probably wrong with your code:
>>> 1. You are calling 'principal' from inside __init__ so you never actually
>>> return from __init__ which means that you never call "window.show()" and
>>> therefore never call "qApp.exec_()". If you really want to use the
>>> 'principal' method you would have to connect it to a one shot timer anyway
>>> to have it run after you have started the application ('qApp.exec_()'). I
>>> think the recommended way would be to use the timer the way you did in your
>>> latest email.
>>>
>>> 2. At least in the way my email client reads your original code, your
>>> calls to the matplotlib drawing functions aren't inside the while loop and
>>> the while loop never ends...although this doesn't matter if you don't fix #1
>>> above.
>>>
>>> Hope that made sense.
>>>
>>> -Dave
>>>
>>>
>>> On 12/5/11 1:44 PM, matplotlib-users-requ...@lists.sourceforge.net wrote:
>>>>
>>>> Message: 3
>>>> Date: Mon, 5 Dec 2011 15:46:02 +0100
>>>> From: Fabien Lafont<lafont.fab...@gmail.com>
>>>> Subject: Re: [Matplotlib-users] [ploting data] Live data
>>>> Cc:matplotlib-users@lists.sourceforge.net
>>>> Message-ID:
>>>>
>>>> <CAC9H_cjrgQBE6e6+jzZHyfYHonTeAg0XwU7c_2G-hu=s+z7...@mail.gmail.com>
>>>> Content-Type: text/plain; charset=ISO-8859-1
>>>>
>>>> Thx all for your remarks,
>>>>
>>>> I can't understand why this code works (when I use the timer method):
>>>
>>>
>>>
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