How to avoid creating the same window in wxPython?

Question

I am creating an application that will have several windows. However, most of the windows should be created only one time. If window B already exists then instead of creating a new window B, the existing window B should be shown. It may be that window B was created but then destroyed and then, of course, I have to create window B again.

The problem is that I cannot find a way to know if windows B exists.

In the example below from the "Initial Window" you can create as many secondary windows as you want. I need a way to make sure that only one secondary window exists at a given time.

I am using Phython3.7 and wxPython 4.0.3

import wx


class FrameA(wx.Frame):

    def __init__(self, parent, title):

        super().__init__(parent, title=title)

        self.i = 1

        self.panel   = wx.Panel(self)
        self.sizer   = wx.GridBagSizer(1, 1)

        self.buttonUtil = wx.Button(self.panel, label='New Window')

        self.sizer.Add(self.buttonUtil, pos=(0, 0))

        self.panel.SetSizer(self.sizer) 

        self.buttonUtil.Bind(wx.EVT_BUTTON, self.Util)

        self.Centre()

    def Util(self, event):

        frame = FrameB(None, title=str(self.i))
        frame.Show()
        self.i += 1

class FrameB(wx.Frame):

    def __init__(self, parent, title):

        super().__init__(parent, title=title)


app = wx.App()
frameA = FrameA(None, title='Initial Window')
frameA.Show()
app.SetTopWindow(frameA)
app.MainLoop()

Answer 1

Store created FrameB in an object variable in FrameA, e.g. as self.frame. In FrameA constructor initialize this variable to None.

In constructor of FrameB add parameter to store the creating FrameA (if multiple can exist). Then bind to close event to set frame of creating FrameA to None if B is closed.

In Util() check first if frame is None. If so, create new FrameB and assign it to self.frame. Otherwise focus existing B.