You can use wx.GCDC because it support anti-aliased drawing
Try this:
buffer = wx.EmptyBitmap(500,500) # creating empty buffer
dc = wx.MemoryDC(buffer) # to handle the buffer
dc = wx.GCDC(dc)
dc.SetBackground( wx.Brush("White") ) # setting background
dc.DrawCircle(50,40,100) #drawing circle
dc.DrawCircle(200,200,100) #drawing circle