Question

I am creating a menu and assigning images to menu items, sometime first item in menu doesn’t display any image, I am not able to find the reason. I have tried to make a simple stand alone example and below is the code which does demonstrates the problem on my machine.
I am using windows XP, wx 2.8.7.1 (msw-unicode)’

import wx

def getBmp():
    bmp = wx.EmptyBitmap(16,16)
    return bmp

class MyFrame(wx.Frame):
    def __init__(self):
        wx.Frame.__init__(self, style=wx.DEFAULT_FRAME_STYLE, parent=None)

        self.SetTitle("why New has no image?")

        menuBar = wx.MenuBar()
        fileMenu=wx.Menu()
        item = fileMenu.Append(wx.ID_NEW, "New")
        item.SetBitmap(getBmp())
        item = fileMenu.Append(wx.ID_OPEN, "Open")
        item.SetBitmap(getBmp())
        item = fileMenu.Append(wx.ID_SAVE, "Save")
        item.SetBitmap(getBmp())
        menuBar.Append(fileMenu, "File")
        self.SetMenuBar(menuBar) 


app = wx.PySimpleApp()
frame=MyFrame()
frame.Show()
app.SetTopWindow(frame)
app.MainLoop()

So are you able to see the problem and what could be the reason for it?

Conclusion: Yes this is a official bug, I have created a simple Menu class to overcome this bug, using the trick given by “balpha” in selected answer

It overrides each menu.Append method and sees if menu item with image is being added for first time, if yes creates a dummy item and deletes it later.

This also adds feature/constraint so that instead of calling SetBitmap, you should pass bitmap as optional argument image

import wx

class MockMenu(wx.Menu):
    """
    A custom menu class in which image param can be passed to each Append method
    it also takes care of bug http://trac.wxwidgets.org/ticket/4011
    """

    def __init__(self, *args, **kwargs):
        wx.Menu.__init__(self, *args, **kwargs)
        self._count = 0

    def applyBmp(self, unboundMethod, *args, **kwargs):
        """
        there is a bug in wxPython so that it will not display first item bitmap
        http://trac.wxwidgets.org/ticket/4011
        so we keep track and add a dummy before it and delete it after words
        may not work if menu has only one item
        """

        bmp = None
        if 'image' in kwargs:
            bmp = kwargs['image']

        tempitem = None
        # add temp item so it is first item with bmp 
        if bmp and self._count == 1:
            tempitem = wx.Menu.Append(self, -1,"HACK")
            tempitem.SetBitmap(bmp)

        ret = unboundMethod(self, *args, **kwargs)
        if bmp:
            ret.SetBitmap(bmp)

        # delete temp item
        if tempitem is not None:
            self.Remove(tempitem.GetId())

        self._lastRet = ret
        return ret

    def Append(self, *args, **kwargs):
        return self.applyBmp(wx.Menu.Append, *args, **kwargs)

    def AppendCheckItem(self, *args, **kwargs):
        return self.applyBmp(wx.Menu.AppendCheckItem, *args, **kwargs)

    def AppendMenu(self, *args, **kwargs):
        return self.applyBmp(wx.Menu.AppendMenu, *args, **kwargs)

Answer 1

This is a confirmed bug which appearently has been open for quite a while. After trying around a little bit, this workaround seems to do it:

    menuBar = wx.MenuBar()
    fileMenu=wx.Menu()
    tempitem = fileMenu.Append(-1,"X")       # !!!
    tempitem.SetBitmap(getBmp())             # !!!
    item = fileMenu.Append(wx.ID_NEW, "New")
    fileMenu.Remove(tempitem.GetId())        # !!!
    item.SetBitmap(getBmp())
    item = fileMenu.Append(wx.ID_OPEN, "Open")
    item.SetBitmap(getBmp())
    item = fileMenu.Append(wx.ID_SAVE, "Save")
    item.SetBitmap(getBmp())
    menuBar.Append(fileMenu, "File")
    self.SetMenuBar(menuBar) 

Note that the position of the fileMenu.Remove call is the earliest position that works, but you can also move it to the bottom. HTH.