how do i get the pivot point of a given mesh; how can i control it; or just modify.If there is a property and a method related to it plz tell me, i have probe almost everything.

so, the mesh has its own coordinate space… a local X axis, Y axis and Z axis. It also has a local origin. The pivot of a mesh is the local origin

to move the origin of a mesh around without relative to the mesh verticies, you need to move the mesh verticies in the opposite direction. The same applies to rotation and stuff. If you want the post-transform [location scale and rotation] position of the verticies to not change then you must also move the object around.

umm, this is incredibly obvious once you “get it”… but it is kind of hard to explain

i dont know if a really understand it, but i will make and effort.
that kind of information is not easy to find in those helps file or the blender api. well thx!