wxPython - Panel doesn't cover all frame on show if frame full screen

If I resize the window and I make it full screen again I get the result I desire:

Before

After resize window and full screen

The panel is the one on the far right with a more black grey color. I have the panel and a mainframe where I show the panel inside doing:

def __init_new_trading_bot_panel(self):
    self.__remove_all_panels()
    self.__mNewBotPanel = NewTradingBotPanel(self, wx.DisplaySize())
    self.__mNewBotPanel.Show()

Makes no sense to me, I tried to add an EVT_SHOW on the panel to do a Update after it renderized but it doesn't work too.

Code panel:

import wx, threading
from Resources.Strings import Strings
from Resources.Constants import Constants, Sizes

class NewTradingBotPanel(wx.Panel, threading.Thread):

    __mMainBox: wx.BoxSizer = None
    __mSecondBox: wx.BoxSizer = None
    __mRightPanel: wx.Panel = None

    __mtxMaxDayChange: wx.TextCtrl = None
    __mtxMinDayChange: wx.TextCtrl = None
    __mtxMaxMarketCap: wx.TextCtrl = None
    __mtxMinMarketCap: wx.TextCtrl = None
    __mtxMaxDayRange: wx.TextCtrl = None
    __mtxMinDayRange: wx.TextCtrl = None
    __mtxMaxWeekRange: wx.TextCtrl = None
    __mtxMinWeekRange: wx.TextCtrl = None
    __mtxMaxMonthRange: wx.TextCtrl = None
    __mtxMinMonthRange: wx.TextCtrl = None
    __mtxMaxYearRange: wx.TextCtrl = None
    __mtxMinYearRange: wx.TextCtrl = None
    __mtxMaxDayVolume: wx.TextCtrl = None
    __mtxMinDayVolume: wx.TextCtrl = None
    __mtxMaxCompanyValue: wx.TextCtrl = None
    __mtxMinCompanyValue: wx.TextCtrl = None
    __mtxMaxRatioCompanyValueMarketCap: wx.TextCtrl = None
    __mtxMinRatioCompanyValueMarketCap: wx.TextCtrl = None
    __mtxMaxBeta: wx.TextCtrl = None
    __mtxMinBeta: wx.TextCtrl = None
    __mtxMaxRatioPE: wx.TextCtrl = None
    __mtxMinRatioPE: wx.TextCtrl = None
    __mtxMaxEPS: wx.TextCtrl = None
    __mtxMinEPS: wx.TextCtrl = None
    __mtxMaxYearTarget: wx.TextCtrl = None
    __mtxMinYearTarget: wx.TextCtrl = None
    __mtxMaxTrailingPE: wx.TextCtrl = None
    __mtxMinTrailingPE: wx.TextCtrl = None
    __mtxMaxForwardPE: wx.TextCtrl = None
    __mtxMinForwardPE: wx.TextCtrl = None
    __mtxMaxPegRatio: wx.TextCtrl = None
    __mtxMinPegRatio: wx.TextCtrl = None
    __mtxMaxPriceSales: wx.TextCtrl = None
    __mtxMinPriceSales: wx.TextCtrl = None
    __mtxMaxPriceBook: wx.TextCtrl = None
    __mtxMinPriceBook: wx.TextCtrl = None
    __mtxMaxCompanyValueRevenue: wx.TextCtrl = None
    __mtxMinCompanyValueRevenue: wx.TextCtrl = None
    __mtxMaxCompanyValueEbitda: wx.TextCtrl = None
    __mtxMinCompanyValueEbitda: wx.TextCtrl = None

    def __init__(self, parent, size):
        wx.Panel.__init__(self, parent, size=size)
        threading.Thread.__init__(self)
        self.__init_layout()

#region - Private Methods
#region - Init Methods
    def __init_layout(self):
        self.__mMainBox = wx.BoxSizer(wx.HORIZONTAL)
        self.__mMainBox.AddSpacer(15)
        
        self.__mSecondBox = wx.BoxSizer(wx.VERTICAL)
        self.__mSecondBox.AddSpacer(15)
        self.__init_first_box_sizer()
        self.__mSecondBox.AddSpacer(15)
        self.__init_second_box_sizer()
        self.__mSecondBox.AddSpacer(15)
        self.__init_third_box_sizer()
        self.__mSecondBox.AddSpacer(15)
        self.__init_fourth_box_sizer()
        self.__mSecondBox.AddSpacer(15)
        self.__init_fifth_box_sizer()
        self.__mSecondBox.AddSpacer(15)

        self.__mMainBox.Add(self.__mSecondBox, 1, wx.ALL | wx.EXPAND)
        self.__init_right_panel()
        self.__mMainBox.Add(self.__mRightPanel, 1, wx.ALL | wx.EXPAND)

        self.SetSizer(self.__mMainBox)
        self.Update()

    def __init_first_box_sizer(self):
        boxSizer = wx.BoxSizer(wx.HORIZONTAL)
        boxSizer.AddSpacer(15)
        panel = wx.Panel(self)
        panel.SetBackgroundColour((75, 75, 75))
        self.__mSecondBox.Add(panel, 1, wx.ALL | wx.EXPAND)
        boxSizer.Add(self.__get_boxsizer_day_change(panel))
        boxSizer.AddSpacer(50)
        boxSizer.Add(self.__get_boxsizer_day_change(panel))
        boxSizer.AddSpacer(50)
        boxSizer.Add(self.__get_boxsizer_day_change(panel))
        boxSizer.AddSpacer(50)
        boxSizer.Add(self.__get_boxsizer_day_change(panel))
        boxSizer.AddSpacer(50)
        boxSizer.Add(self.__get_boxsizer_day_change(panel))
        boxSizer.AddSpacer(50)
        panel.SetSizer(boxSizer)

    def __init_second_box_sizer(self):
        boxSizer = wx.BoxSizer(wx.HORIZONTAL)
        boxSizer.AddSpacer(15)
        panel = wx.Panel(self)
        panel.SetBackgroundColour((75, 75, 75))
        self.__mSecondBox.Add(panel, 1, wx.ALL | wx.EXPAND)
        boxSizer.Add(self.__get_boxsizer_day_change(panel))
        boxSizer.AddSpacer(50)
        boxSizer.Add(self.__get_boxsizer_day_change(panel))
        boxSizer.AddSpacer(50)
        boxSizer.Add(self.__get_boxsizer_day_change(panel))
        boxSizer.AddSpacer(50)
        boxSizer.Add(self.__get_boxsizer_day_change(panel))
        boxSizer.AddSpacer(50)
        boxSizer.Add(self.__get_boxsizer_day_change(panel))
        boxSizer.AddSpacer(50)
        panel.SetSizer(boxSizer)

    def __init_third_box_sizer(self):
        boxSizer = wx.BoxSizer(wx.HORIZONTAL)
        boxSizer.AddSpacer(15)
        panel = wx.Panel(self)
        panel.SetBackgroundColour((75, 75, 75))
        self.__mSecondBox.Add(panel, 1, wx.ALL | wx.EXPAND)
        boxSizer.Add(self.__get_boxsizer_day_change(panel))
        boxSizer.AddSpacer(50)
        boxSizer.Add(self.__get_boxsizer_day_change(panel))
        boxSizer.AddSpacer(50)
        boxSizer.Add(self.__get_boxsizer_day_change(panel))
        boxSizer.AddSpacer(50)
        boxSizer.Add(self.__get_boxsizer_day_change(panel))
        boxSizer.AddSpacer(50)
        boxSizer.Add(self.__get_boxsizer_day_change(panel))
        boxSizer.AddSpacer(50)
        panel.SetSizer(boxSizer)

    def __init_fourth_box_sizer(self):
        boxSizer = wx.BoxSizer(wx.HORIZONTAL)
        boxSizer.AddSpacer(15)
        panel = wx.Panel(self)
        panel.SetBackgroundColour((75, 75, 75))
        self.__mSecondBox.Add(panel, 1, wx.ALL | wx.EXPAND)
        boxSizer.Add(self.__get_boxsizer_day_change(panel))
        boxSizer.AddSpacer(50)
        boxSizer.Add(self.__get_boxsizer_day_change(panel))
        boxSizer.AddSpacer(50)
        boxSizer.Add(self.__get_boxsizer_day_change(panel))
        boxSizer.AddSpacer(50)
        boxSizer.Add(self.__get_boxsizer_day_change(panel))
        boxSizer.AddSpacer(50)
        boxSizer.Add(self.__get_boxsizer_day_change(panel))
        boxSizer.AddSpacer(50)
        panel.SetSizer(boxSizer)

    def __init_fifth_box_sizer(self):
        boxSizer = wx.BoxSizer(wx.HORIZONTAL)
        boxSizer.AddSpacer(15)
        panel = wx.Panel(self)
        panel.SetBackgroundColour((75, 75, 75))
        self.__mSecondBox.Add(panel, 1, wx.ALL | wx.EXPAND)
        boxSizer.Add(self.__get_boxsizer_day_change(panel))
        boxSizer.AddSpacer(50)
        boxSizer.Add(self.__get_boxsizer_day_change(panel))
        boxSizer.AddSpacer(50)
        boxSizer.Add(self.__get_boxsizer_day_change(panel))
        boxSizer.AddSpacer(50)
        boxSizer.Add(self.__get_boxsizer_day_change(panel))
        boxSizer.AddSpacer(50)
        boxSizer.Add(self.__get_boxsizer_day_change(panel))
        boxSizer.AddSpacer(50)
        panel.SetSizer(boxSizer)

    def __init_right_panel(self):
        self.__mRightPanel = wx.Panel(self)
        self.__mRightPanel.SetBackgroundColour((55, 55, 55))
        self.__mRightPanel.SetSize((-1, -1))

        hbs = wx.BoxSizer(wx.HORIZONTAL)
        hbs.AddSpacer(25)
        
        vbs = wx.BoxSizer(wx.VERTICAL)
        vbs.AddSpacer(25)
        static = wx.StaticText(self.__mRightPanel, label = "Settings To Create a BOT", style = wx.ALIGN_CENTRE)
        vbs.Add(static, 0, wx.EXPAND, 50)
        static.Wrap(self.__mRightPanel.Size[0])
        hbs.Add(vbs)
        
        hbs.AddSpacer(25)

        self.__mRightPanel.SetSizer(hbs)

#endregion

#region - BoxSizer Day Change Methods
    def __get_boxsizer_day_change(self, panel):
        bsDayChange = wx.BoxSizer(wx.VERTICAL)
        bsDayChange.Add(self.__get_boxsizer_max_day_change(panel))
        bsDayChange.AddSpacer(Sizes.SPACER_TRADING_BOT_PANEL_GRID)
        bsDayChange.Add(self.__get_boxsizer_min_day_change(panel))
        return bsDayChange

    def __get_boxsizer_max_day_change(self, panel):
        self.__mtxMaxDayChange = wx.TextCtrl(panel, wx.ID_ANY, value = "", size = Sizes.INPUT_TEXT_SIZE_NEW_TRADING_BOT_PANEL)
        bsMaxDayChange = wx.BoxSizer(wx.VERTICAL)
        bsMaxDayChange.Add(wx.StaticText(panel, label = Strings.STR_MAX_DAY_CHANGE, style = wx.ALIGN_CENTRE), 0, wx.EXPAND)
        bsMaxDayChange.Add(self.__mtxMaxDayChange, 0, wx.EXPAND)
        return bsMaxDayChange

    def __get_boxsizer_min_day_change(self, panel):
        self.__mtxMinDayChange = wx.TextCtrl(panel, wx.ID_ANY, value = "", size = Sizes.INPUT_TEXT_SIZE_NEW_TRADING_BOT_PANEL)
        bsMinDayChange = wx.BoxSizer(wx.VERTICAL)
        bsMinDayChange.Add(wx.StaticText(panel, label = Strings.STR_MIN_DAY_CHANGE, style = wx.ALIGN_CENTRE), 0, wx.EXPAND)
        bsMinDayChange.Add(self.__mtxMinDayChange, 0, wx.EXPAND)
        return bsMinDayChange
#endregion

#region - BoxSizer Market Cap Methods
    def __get_boxsizer_market_cap(self):
        bsMarketCap = wx.BoxSizer(wx.VERTICAL)
        bsMarketCap.Add(self.__get_boxsizer_max_market_cap())
        bsMarketCap.AddSpacer(Sizes.SPACER_TRADING_BOT_PANEL_GRID)
        bsMarketCap.Add(self.__get_boxsizer_min_market_cap())
        return bsMarketCap
        
    def __get_boxsizer_max_market_cap(self):
        self.__mtxMaxMarketCap = wx.TextCtrl(self, wx.ID_ANY, value = "", size = Sizes.INPUT_TEXT_SIZE_NEW_TRADING_BOT_PANEL)
        bsMaxMarketCap = wx.BoxSizer(wx.VERTICAL)
        bsMaxMarketCap.Add(wx.StaticText(self, label = Strings.STR_MAX_MARKET_CAP, style = wx.ALIGN_CENTRE), 0, wx.EXPAND)
        bsMaxMarketCap.Add(self.__mtxMaxMarketCap, 0, wx.EXPAND)
        return bsMaxMarketCap

    def __get_boxsizer_min_market_cap(self):
        self.__mtxMinMarketCap = wx.TextCtrl(self, wx.ID_ANY, value = "", size = Sizes.INPUT_TEXT_SIZE_NEW_TRADING_BOT_PANEL)
        bsMinMarketCap = wx.BoxSizer(wx.VERTICAL)
        bsMinMarketCap.Add(wx.StaticText(self, label = Strings.STR_MIN_MARKET_CAP, style = wx.ALIGN_CENTRE), 0, wx.EXPAND)
        bsMinMarketCap.Add(self.__mtxMinMarketCap, 0, wx.EXPAND)
        return bsMinMarketCap
#endregion

#region - BoxSizer Day Range Methods
    def __get_boxsizer_day_range(self):
        bsDayRange = wx.BoxSizer(wx.VERTICAL)
        bsDayRange.Add(self.__get_boxsizer_max_day_range())
        bsDayRange.AddSpacer(Sizes.SPACER_TRADING_BOT_PANEL_GRID)
        bsDayRange.Add(self.__get_boxsizer_min_day_range())
        return bsDayRange

    def __get_boxsizer_max_day_range(self):
        self.__mtxMaxDayRange = wx.TextCtrl(self, wx.ID_ANY, value = "", size = Sizes.INPUT_TEXT_SIZE_NEW_TRADING_BOT_PANEL)
        bsMaxDayRange = wx.BoxSizer(wx.VERTICAL)
        bsMaxDayRange.Add(wx.StaticText(self, label = Strings.STR_MAX_DAY_RANGE, style = wx.ALIGN_CENTRE), 0, wx.EXPAND)
        bsMaxDayRange.Add(self.__mtxMaxDayRange, 0, wx.EXPAND)
        return bsMaxDayRange

    def __get_boxsizer_min_day_range(self):
        self.__mtxMinDayRange = wx.TextCtrl(self, wx.ID_ANY, value = "", size = Sizes.INPUT_TEXT_SIZE_NEW_TRADING_BOT_PANEL)
        bsMinDayRange = wx.BoxSizer(wx.VERTICAL)
        bsMinDayRange.Add(wx.StaticText(self, label = Strings.STR_MIN_DAY_RANGE, style = wx.ALIGN_CENTRE), 0, wx.EXPAND)
        bsMinDayRange.Add(self.__mtxMinDayRange, 0, wx.EXPAND)
        return bsMinDayRange
#endregion
#endregion
        

On the MainFrame I do:

    def __init__(self):
        wx.Frame.__init__(self, None, wx.ID_ANY, title=Strings.STR_TRADING_BOT, size=Constants.DISPLAY_SIZE_MAIN_FRAME)
        wx.Frame.CenterOnScreen(self)
        self.Maximize(True)
        self.Show()
        self.__init_layout()

    def OnCloseMe(self, event):
        self.Close(True)

    def OnCloseWindow(self, event):
        self.Destroy()

I expect the panel to show full screen on start without resizing the window

If I remove the right panel I get the same with other little panels on vertical until I resize the window and make it again full screen.

BEFORE RESIZE AND FULL SCREEN WITHOUT RIGHT PANEL

(The Light grey should take all the screen in horizontal)

Solved with:

self.Fit() 

on the Panel init:

def __init__(self, parent, size):
        wx.Panel.__init__(self, parent, size=size)
        threading.Thread.__init__(self)
        self.__init_layout()


def __init_layout(self):
        [.. Code ..]
        self.Update()
        self.Fit()                 # HERE AFTER UPDATE

Result on first launch:

Check answer here for more info and a solution about other problems I found on the same program: wxPython - Panels become right only after Window Resized