[Tutor] how can a value be retrieved from an event loop?

[Alan Gauld]

On 16/11/2023 10:31, Phil wrote:

> What I have in mind is to have the knob class return values to the
> instance app and use it just like a scale widget.
> 
> To set an angle from the instance code this is what I have done:

I'm slight confused by your terminology here.
A class is a template from which you create instances.
Instances present an API to which you can send "messages"
(aka call functions) Those functions are implemented
in the class definition but each instance offers them
independently.

So I don't really understand what you mean by the class
returns values to the instance app? The class creates
an instance. The instances should return values.

> knob.set_angle(15) which does set the angle but only once I've clicked
> on the knob and started the event loop.
> 
> So, should I call turn_clockwise() before I call knob.set() and what
> arguments should I pass to the turn method? If so, that seems a bit
> clumsy. I don't have to do anything like that to get values from a scale
> widget.

Getting values should be straightforward. It's setting them
that's hard. At least, making the new value display is
hard, just setting the value is easy.

I still don't understand what it is that you are trying to
do that requires you to set/get values of widgets outside
the mainloop? Apart from initialising the widgets (which should
be inside the __init__), anything you need to do should be
possible inside the loop. It seems like you are fighting
the framework for no obvious purpose. The event loop is there
to make your life easier, why not use it?

-- 
Alan G
Author of the Learn to Program web site
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