Qt: Style depending on label value - qt

Question

I have what looks like a very simple problem: I want to design a QLabel whose value changes dynamically (no issue here) and whose background color changes accordingly (this is the issue).
Of course, I know I can do something like that (pseudo code):
function on_new_value(value):
label.setText(value)
if value>10:
label.setBackgroundColor(RED)
else if value<0:
label.setBackgroundColor(RED)
else:
label.setBackgroundColor(GREEN)
But that kind of mixes model and view. What I'd like, ideally, would be to be able to use an extended version of Qt Stylesheets as follows:
QLabel { background: green; }
QLabel { if value>10: background: red; }
QLabel { if value<0: background: red; }
Obviously, that is not possible. But I'm wondering if Qt allows for something close in order to embbed (for instance in a class) a graphic behaviour based on a value.
I know about QPalette, but the style condition is only about the widget Active/Disable state, not its "value".
In other words, I'm looking for sort of a ValueDependantStyle class or somehting close.
Any pointers? Am I looking at this all wrong?
Edit: in case this is important, I'm developping with PyQt5.

Answer 1

You could use a "model property" on the label, that defines the color in a style sheet (cf. Qt Style Sheet Reference about properties):
function on_new_value(value):
label.setText(value)
if value>10:
label.setProperty("HasError", "true")
else if value<0:
label.setProperty("HasError", "true")
else:
label.setProperty("HasError", "false")
QLabel[HasError="false"] { background: green; }
QLabel[HasError="true"] { background: red; }