Python GUI guizero: basic Colour Picker

# This Python code implements a basic Colour Picker.
# Colours are specified in RGB format. Hex "#rrggbb" is generated.
# It is a demo of the GUI guizero (with Slider command)
#
# guizero works with tkinter but simpler with extra widgets eg. Slider
# https://lawsie.github.io/guizero/slider/
# nb. Slider contains tkinter.Scale

from guizero import App, Box, Text, TextBox, Slider, Drawing
app = App( height=680, width=500)
#-------------------- -------------------
def getHexColorString(iRed, iGreen, iBlue): # PREcondition: 0..255 (x00..xFF)
    # gigo .. allow to fail ! No range check.
    xRed   = "{0:02X}".format(iRed)
    xGreen = "{0:02X}".format(iGreen)
    xBlue  = "{0:02X}".format(iBlue)

    return '#' + xRed + xGreen + xBlue
#----------------------------------------

def colorChange(): # 0..255 (xFF)
    # values from Slider with (end=255)
    #-------------------
    # get full color code "#rrggbb"
    newColor =  getHexColorString( redSlider.value, greenSlider.value, blueSlider.value )
    #           -----------------
    ################
    # notify Views #
    # ------------ #
    # set color in pane
    colorPane.bg = newColor

    # notify hex values (to Views)
    colorHexText.value     = newColor
    colorHexTextCOPY.value = newColor
    # extract color-component hex values from color-string using a slice [:] for sub-strings
    redHex.value   = newColor[1:3]
    greenHex.value = newColor[3:5]
    blueHex.value  = newColor[5:7]

#---------------
# add widgets ..
h1 = Text(app, text="Colour Picker", size=26, font="Times New Roman")
##   ----
colorWidget = Box(app, border=1)
#-------------------------------
colorControls = Box(colorWidget)
#------------------
redControl   = Box(colorControls, height="fill", align="left")
redHex = Text(redControl)
redHex.text_color = "red"
redSlider = Slider(redControl, end=255, command= colorChange, horizontal=False)
redSlider.bg = "red"
redSlider.text_color = "white"
#-----------------
greenControl = Box(colorControls, height="fill", align="left")
greenHex = Text(greenControl)
greenHex.text_color = "green"
greenSlider = Slider(greenControl, end=255, command= colorChange, horizontal=False)
greenSlider.bg = "green"
greenSlider.text_color = "white"
#-----------------
blueControl  = Box(colorControls, height="fill", align="left")
blueHex = Text(blueControl)
blueHex.text_color = "blue"
blueSlider = Slider(blueControl, end=255, command= colorChange, horizontal=False)
blueSlider.bg = "blue"
blueSlider.text_color = "white"
#-------------------------------
# other Views ..
colorHexText = Text(colorWidget)
colorPane = Drawing(colorWidget, width=500, height="fill")

colorHexCOPYlabel = Text(colorWidget, text="To COPY 'color-text' use: [Ctrl A] .. then .. [Ctrl C]")
colorHexTextCOPY = TextBox(colorWidget)
colorHexTextCOPY.width = 8 # chars
colorHexTextCOPY.bg="white"
colorHexTextCOPY.text_size = 18
#-------------------------
#set initial RGB Slider values ..
redSlider.value   =  75
greenSlider.value = 255
blueSlider.value  = 146
colorChange()

colorHexTextCOPY.focus()  # ready to COPY
app.display()