Positioning Buttons with sizers

# google groups: wxpython-users
# topic replied to: Curious why this alignment has to be set up this way

# http://www.blog.pythonlibrary.org/2011/01/04/wxpython-wx-listctrl-tips-and-tricks/

import wx

# you could use collections.OrderedDict
data = {
    # map
    # sort_key, count, greek
    5:('one', 'alpha'),
    6:('two', 'beta'),
    7:('three', 'gamma'),
    8:('four', 'delta'), }


class MainPanel(wx.Panel):

    __doc__ = wx.Panel.__doc__

    # Panel(parent, id=ID_ANY, pos=DefaultPosition, size=DefaultSize, style=TAB_TRAVERSAL, name=PanelNameStr)
    def __init__(self, parent, id=wx.ID_ANY, pos=wx.DefaultPosition, size=wx.DefaultSize, style=wx.TAB_TRAVERSAL, name='MainPanel'):
        #wx.Panel.__init__(self, parent, id, pos, size, style, name)
        super().__init__(parent, id, pos, size, style, name)

        # Add three buttons
        # Button(parent, id=ID_ANY, label=EmptyString, pos=DefaultPosition, size=DefaultSize, style=0, validator=DefaultValidator, name=ButtonNameStr)
        ok = wx.Button(self, id=wx.ID_OK, name='ok')
        cancel = wx.Button(self, id=wx.ID_CANCEL, name='cancel')
        exitb = wx.Button(self, id=wx.ID_EXIT, name='exit')

        # Put three buttons into a BoxSizer
        hsizer = wx.BoxSizer(wx.HORIZONTAL)
        hsizer.Add(ok, 0, wx.ALIGN_RIGHT | wx.EXPAND | wx.ALL, 5)
        hsizer.Add(cancel, 0, wx.ALIGN_RIGHT | wx.EXPAND | wx.ALL, 5)
        hsizer.Add(exitb, 0, wx.ALIGN_RIGHT | wx.EXPAND | wx.ALL, 5)

        # ListCtrl(parent, id=ID_ANY, pos=DefaultPosition, size=DefaultSize, style=LC_ICON, validator=DefaultValidator, name=ListCtrlNameStr)
        self.lb = wx.ListCtrl(self, style = wx.LC_REPORT | wx.BORDER_SUNKEN | wx.LC_SINGLE_SEL, name='mylist')
        self.lb.InsertColumn(0, 'Count')
        self.lb.InsertColumn(1, 'Greek')

        # Fill the ListCtrl
        self.fillListCtrl()

        # Layout buttons and ListCtrl
        vsizer = wx.BoxSizer(wx.VERTICAL)
        vsizer.Add(hsizer, 0, wx.ALIGN_RIGHT | wx.ALL, 0)
        vsizer.Add(self.lb, 1, wx.EXPAND | wx.ALL, 5)

        self.SetSizer(vsizer)

        self.setListCtrlColumnWidths()

        # Event Bindings
        self.Bind(wx.EVT_SIZE, self.onSize)
        self.Bind(wx.EVT_BUTTON, self.onButton)
        self.Bind(wx.EVT_LIST_ITEM_SELECTED, self.onItemSelected)


    def fillListCtrl(self, start=0, end=None):

        """NotImplemented start and end"""

        self.lb.DeleteAllItems()
        index = 0
        for key in sorted(data):
            label = data[key][0]
            greek = data[key][1]
            item = self.lb.InsertItem(index, label)
            self.lb.SetItem(index, 1, greek)

            # optional for sorting
            self.lb.SetItemData(index, key)
            index += 1


    def setListCtrlColumnWidths(self):

        """Set the listctrl column zero's width to the remaining
        width after column one's usage. Magic number 5 removed from
        width to prevent horizontal scrollbar."""

        second_column_width = self.lb.GetColumnWidth(1)
        first_column_width = self.lb.GetSize()[0]-5-second_column_width
        self.lb.SetColumnWidth(0, first_column_width)


    def SetStatusText(self, text='', number=0):
        top_parent = self.GetTopLevelParent()
        if top_parent.GetStatusBar():
            top_parent.SetStatusText(text, number)


    def onItemSelected(self, event):
        index = event.GetIndex()
        key = event.GetData()
        label = event.GetLabel()


        column_1_text = data[key][1]
        # OR
        column_1_item  = self.lb.GetItem(index, 1)
        column_1_text = column_1_item.GetText()

        text = "index:{} sort_key:{} count:{} greek:{}".format(
            index, key, label, column_1_text)
        self.SetStatusText(text)


    def onSize(self, event):

        """If you like column zero of the listctrl to expand
        instead of the last column."""

        self.setListCtrlColumnWidths()
        event.Skip() # needed in this case


    def onButton(self, event):
        widget = event.GetEventObject()
        name = widget.GetName()
        self.SetStatusText(name + ' clicked')


class MainFrame(wx.Frame):

    __doc__ = wx.Frame.__doc__

    # Frame(parent, id=ID_ANY, title=EmptyString, pos=DefaultPosition, size=DefaultSize, style=DEFAULT_FRAME_STYLE, name=FrameNameStr)
    def __init__(self, parent, id=wx.ID_ANY, title=wx.EmptyString, pos=wx.DefaultPosition, size=wx.DefaultSize, style=wx.DEFAULT_FRAME_STYLE, name='MainFrame'):

        #wx.Panel.__init__(self, parent, id, pos, size, style, name)
        super().__init__(parent, id, title, pos, size, style, name)

        sizer = wx.BoxSizer(wx.VERTICAL)
        sizer.Add(MainPanel(self), 1, wx.EXPAND | wx.ALL, 0)
        self.SetSizer(sizer)
        self.CreateStatusBar()
        self.Show()


if __name__ == "__main__":
    app = wx.App()
    frame = MainFrame(None, title='BoxSizer options')
    app.MainLoop()