From demo>Layout
The wx.GridBagSizer is more or less a port of the the RowColSizer (that has been in the wxPython.lib package for quite some time) to C++. It allows items to be placed at specific layout grid cells, and items can span across more than one row or column.
RowColSizer
A pure-Python Sizer that lays out items in a grid similar to
wx.FlexGridSizer but item position is not implicit but explicitly
specified by row and col, and row/col spanning is supported.
Adapted from code by Niki Spahiev.
NOTE: There is now a C++ version of this class that has been wrapped
as wx.GridBagSizer. It is quicker and more capable so you are
encouraged to switch.
Jean-Michel Fauth, Switzerland