Maya Python scripting – Getting an object’s transform matrix relative to another object’s coordinates

Software:
Maya 2018

How to get an object transformation matrix relative to another object’s coordinates:
* The following script requires selecting 2 objects, the function will return the transform matrix of the first object relative to the transform matrix of the second.

from maya.api.OpenMaya import MVector, MMatrix, MPoint
import maya.cmds as cmds

def get_relative_transform (node,coordinate_space_node):
    node_matrix = MMatrix(cmds.xform(node, q=True, matrix=True, ws=True))
    parent_matrix = MMatrix(cmds.xform(coordinate_space_node, q=True, matrix=True, ws=True))
    return (node_matrix * parent_matrix.inverse())

node_a = (cmds.ls(sl=1,sn=True))[0]
node_b = (cmds.ls(sl=1,sn=True))[1]

print (get_relative_transform(node_a,node_b))