How to clear a wxPython wx.MemDC to transparent?

Coding
1

Does anyone know how to .Clear( ) a wx.MemDC device context to be transparent? The MemDC is 32 bpp. When I set the background brush to something like:

wx.MemDC.SetBackgroundBrush( wx.Brush( wx.Colour( 0, 0, 0, wx.TRANSPARENT ) ) )

when the memDC is blit’d to the screen it comes in opaque.

2

Couple maybe-relevant threads on the wxPython Users list:
http://groups.google.com/group/wxpython-users/browse_thread/thread/2e776d5fd8e7fe95/e9c45d85b6e28378
http://groups.google.com/group/wxpython-users/browse_thread/thread/f41e67b63dc18de/194c14d81781f2b8

Few years old, however.