>>> g = ogr.CreateGeometryFromWkt('POLYGON((20 0,20 50,80 50,80 0,20 0))')
>>> g
<ogr.GeometryPtr; proxy of C++ OGRGeometryShadow instance at _0060dc60_p_OGRGeometryShadow>

>>> g.ExportToWkb().encode('hex')
'000000000300000001000000054034000000000000000000000000000040340000000000004049000000000000405400000000000040490000000000004054000000000000000000000000000040340000000000000000000000000000'