Pyqtgraph ColorBarItem Add String Next to Number

The following code is a simple modification of the pyqtgraph example "Matrix Display".

import pyqtgraph as pg
from pyqtgraph.Qt import QtWidgets, mkQApp

class MyBar(pg.ColorBarItem):
    def __init__(self, *args, **kargs):
        super().__init__(*args,**kargs)
        self.unit = "cm"
        self.display_unit()
    
    def display_unit(self):
        pass

class MainWindow(QtWidgets.QMainWindow):
    """ example application main window """
    def __init__(self, *args, **kwargs):
        super(MainWindow, self).__init__(*args, **kwargs)
        gr_wid = pg.GraphicsLayoutWidget(show=True)
        self.setCentralWidget(gr_wid)
        self.resize(600,500)
        self.show()

        bar = MyBar( values=(-1,1), colorMap=None)
        gr_wid.addItem(bar)

mkQApp("")
main_window = MainWindow()

if __name__ == '__main__':
    pg.exec()

I have PyQt5 and pyqtgraph installed in my environment. The code runs and gives:

I would like to write a method to add units to my bar. Given a string unit, in this case "cm", I want to achieve any one of two, preferably within this class MyBar, that:

1. The unit gets displayed beside the top number:

2. Add a string, as a title above the whole bar or closely above the top number, which says "unit = cm":

Remark that I am only asking to display an additional string. Nothing in terms of functionality of the bar should change. I tried to go through the source code but had found no way helpful to achieve this.

There actually is a "proper" way to get this to work. pyqtgraph has a built-in automatic handling for axis units, which automatically scales units to the correct SI prefix ('m' for milli-, 'k' for kilo-, etc...). So you just need to grab the ColorBarItem's main axis and give it an appropriate unit.

The one caveat is that 'c' for centi- is not considered an SI prefix py pyqtgraph - it'll automatically go for milli- instead. So, if you want to force it to use "cm" and forego any autoscaling fanciness, you need to call enableAutoSIPrefix(False) on the axis.

import pyqtgraph as pg
from pyqtgraph.Qt import QtWidgets, mkQApp


class MyBar(pg.ColorBarItem):
    def __init__(self, *args, units=None, **kargs):
        super().__init__(*args, **kargs)

        if units is not None:
            self.set_units(units)

    def set_units(self, units):
        self.axis.setLabel(units=units)


class MainWindow(QtWidgets.QMainWindow):
    """ example application main window """

    def __init__(self, *args, **kwargs):
        super(MainWindow, self).__init__(*args, **kwargs)
        gr_wid = pg.GraphicsLayoutWidget(show=True)
        self.setCentralWidget(gr_wid)
        self.resize(600, 500)
        self.show()

        bar = MyBar(values=(-0.01, 0.01), colorMap=None, units="m")
        gr_wid.addItem(bar)


mkQApp("")
main_window = MainWindow()

if __name__ == '__main__':
    pg.exec()