wx python how to place a button on a frame

Question

I have two buttons on a panel. I want one on the left and one on the right. There must be a simple way but I can't see it (the (400, 0) spacer is just an example; it should work on any panel)

import wx


class MainFrame(wx.Frame):
    def __init__(self):
        wx.Frame.__init__(self, None, -1,
                          'Demonstrate wxPython button')
        self.panel = MainPanel(self)
        self.Fit()
        self.Centre()
        self.Show()


class MainPanel(wx.Panel):
    def __init__(self, frame):
        wx.Panel.__init__(self, frame)

        # Button
        button_sizer = self._button_sizer(frame)

        # Main sizer
        main_sizer = wx.BoxSizer(wx.VERTICAL)
        main_sizer.Add((400, 0))
        main_sizer.Add(button_sizer)
        self.SetSizer(main_sizer)
        self.Fit()

    def _button_sizer(self, frame):
        cmd_save = wx.Button(self, wx.ID_SAVE)
        cmd_cancel = wx.Button(self, wx.ID_CANCEL)
        button_sizer = wx.BoxSizer(wx.HORIZONTAL)
        button_sizer.Add(cmd_save)
        button_sizer.Add(cmd_cancel, flag=wx.ALIGN_RIGHT)
        return button_sizer


if __name__ == '__main__':
    screen_app = wx.App()
    main_frame = MainFrame()
    screen_app.MainLoop()

(Sorry about this; StackOverflow want more text)

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Answer 1

I have always found the the sizer element proportion is your friend in cases like these. Which defines how much room a certain element should take up in relation to others.
Here is your code, with the proportion option being used.

import wx
class MainFrame(wx.Frame):
    def __init__(self):
        wx.Frame.__init__(self, None, -1, 'Demonstrate wxPython button')
        self.panel = MainPanel(self)
       # self.Fit()
        self.Centre()
        self.Show()

class MainPanel(wx.Panel):
    def __init__(self, frame):
        wx.Panel.__init__(self, frame)
        # Button
        button_sizer = self._button_sizer(frame)
        # Main sizer
        main_sizer = wx.BoxSizer(wx.VERTICAL)
        main_sizer.Add(button_sizer,proportion=1, flag=wx.EXPAND)
        self.SetSizer(main_sizer)
        self.Fit()

    def _button_sizer(self, frame):
        cmd_save = wx.Button(self, wx.ID_SAVE)
        cmd_cancel = wx.Button(self, wx.ID_CANCEL)
        button_sizer = wx.BoxSizer(wx.HORIZONTAL)
        button_sizer.Add(cmd_save)
        button_sizer.Add((-1, -1), proportion=1)
        button_sizer.Add(cmd_cancel)
        return button_sizer

if __name__ == '__main__':
    screen_app = wx.App()
    main_frame = MainFrame()
    screen_app.MainLoop()