Last time I mentioned Flexx, a pure Python solution to create GUI's in the browser.
It took me some time to get used to the event system used by Flexx, but it is very powerful..

Here is a complete example with 4 sliders controlling ADSR of a csd.

"""
Flexx Csound interface
    zappfinger, 23SEP2018

"""
import sys
sys.path.insert(0, '/Users/richard/py35env/lib/python3.5/site-packages')
from csoundSession import CsoundSession
from flexx import flx, ui, event

class ThemedForm(flx.Widget):   # lives in JS

    def init(self):
        flx.Label(text='Att:')
        self.slider1 = flx.Slider(min=0.01, max=2, value=.5, flex=0)
        flx.Label(text='Dec:')
        self.slider2 = flx.Slider(min=0, max=6, value=0, flex=0)
        flx.Label(text='Sus:')
        self.slider3 = flx.Slider(min=1, max=10, value=5, flex=0)
        flx.Label(text='Rel:')
        self.slider4 = flx.Slider(min=0, max=6, value=0, flex=1)

    @flx.reaction
    def _update(self, *events):
        att, dec, sus, rel = self.slider1.value, self.slider2.value, self.slider3.value, self.slider4.value
        self.root.cses.update(att, dec, sus, rel)


class CsSession(flx.PyComponent):  # Lives in Python
    cs = CsoundSession("/Users/richard/PycharmProjects/OSCall/csds/Mono_Synth.csd")

    @flx.action
    def update(self, *events):
        self.cs.setControlChannel('att', events[0])
        self.cs.setControlChannel('dec', events[1])
        self.cs.setControlChannel('sus', events[2])
        self.cs.setControlChannel('rel', events[3])
        self.cs.setControlChannel('pitchglide', 1.5)


class MyApp(flx.PyComponent):
    cses = flx.ComponentProp()

    def init(self):
        self._mutate_cses(CsSession())
        self.ui = ThemedForm()

if __name__ == '__main__':
    app = flx.App(MyApp)
    app.serve('')
    #m = flx.launch(MyApp, 'chrome-app')
    flx.run()