Trying to capture "OnButtonDown" in GPG Control Paanel

GoPiGo
1

Greetings!

I am attempting to learn more about Python in general, and programming the GoPiGo in particular, by making modifications to the GoPiGo Control Panel within Raspbian for Robots.

Note the following code that I have added to the control panel’s PY file.

Viz.:

        left_button = wx.Button(self, label="Left")
        self.Bind(wx.EVT_BUTTON, self.left_button_OnButtonClick, left_button)
==>     self.Bind(wx.EVT_BUTTON, self.left_button_OnButtonDown, left_button)

Followed by the definition:

    def left_button_OnButtonClick(self,event):
        gpg.left()

==> def left_button_OnButtonDown(self,event):  
        left_button.SetForegroundColour('red')

The idea being that during the interval while the left button is being held down, the text changes color to red.

When I compile the code in Geany, compile succeeds. However when I try to run it, it fails with the following error in the terminal window:

Traceback (most recent call last):
  File "control_panel_gui_3.py", line 284, in left_button_OnButtonDown
    left_button.SetForegroundColour('red')
NameError: global name 'left_button' is not defined

If I add the GLOBAL prefix:

    def left_button_OnButtonDown(self,event):
==>     global left_button    
        left_button.SetForegroundColour('red')

I get this error:

Traceback (most recent call last):
  File "control_panel_gui_3.py", line 284, in left_button_OnButtonDown
    left_button.SetForegroundColour('red')
NameError: global name 'left_button' is not defined

If I prefix “left_button.SetForegroundColor” with “self”:

Traceback (most recent call last):
  File "control_panel_gui_3.py", line 284, in left_button_OnButtonDown
    self.left_button.SetForegroundColour('red')
AttributeError: 'MainPanel' object has no attribute 'left_button'

What I want to do is cause the LEFT button to change color IF it is pressed down and return to its normal colors when released.

Ultimately what I want to do is configure the control panel so that it turns left ONLY when the LEFT button is DOWN, and when it’s released, the 'bot stops.

Obviously, I am not only barking up the wrong tree, I am barking up the wrong tree in the wrong forest!!

The usual on-line Fountains of Wisdom on Python, or wxPython provide zero help whatsoever.

Any advice as to what I am doing wrong would be gratefully appreciated.