I know it is a bad question sorry but I haven't found any information about these matrices expect in the blender documentations.
The docs say that matrix_basis is:
Matrix access to location, rotation and scale (including deltas), before constraints and parenting are applied.
So if not related to any parent, is it the same as matrix_world ?
MW = C.object.matrix_world
into python console and a rep'n of matrix is drawn in 3d view. $\endgroup$