maya_spring_animation.py

import maya.cmds

PARTICLE_DEFAULT_NAME = 'spring_particle'

def setup_spring(obj, time_range = None, spring_weight = 0.5):
    '''
    Sets up spring physics system around a given object

    :param obj: obj to apply physics system to
    :param time_range: time range of animation to process, tuple
    :param spring_weight: weight of spring anim to apply, default 0.5
    :return: True/False
    '''
    if not obj or maya.cmds.objExists(PARTICLE_DEFAULT_NAME):
        return False

    start_frame, end_frame = time_range or [ maya.cmds.playbackOptions(minTime=True, query=True), maya.cmds.playbackOptions(maxTime=True, query=True)]
    maya.cmds.currentTime( start_frame, edit = True )
    locator = maya.cmds.spaceLocator(name='original_animation_locator')
    maya.cmds.particle(p=[(0,0,0)], name=PARTICLE_DEFAULT_NAME)

    # Bake the animation from the selected object to the locator
    locator_constraint = maya.cmds.parentConstraint(obj, locator, mo=False)
    maya.cmds.bakeResults(locator, t=(start_frame, end_frame))
    maya.cmds.delete(locator_constraint)

    # Align the particle with the locator
    #TODO Don't be lazy, do this without a constraint
    align_constraint = maya.cmds.parentConstraint(locator, PARTICLE_DEFAULT_NAME,mo=False)
    maya.cmds.delete(align_constraint)

    # Create a goal for the particle
    maya.cmds.goal(PARTICLE_DEFAULT_NAME, g=locator, w=spring_weight)
    maya.cmds.spaceLocator(name='physics_locator')
    maya.cmds.connectAttr('{0}.worldCentroid'.format(PARTICLE_DEFAULT_NAME), '{0}.translate'.format('physics_locator'))

    point_constraint = maya.cmds.pointConstraint('physics_locator', obj, mo=True, n='physics_point_const')
    return True


def bake_spring(obj, time_range = None):
    '''
    bake an object set up with physics sim. Assumes object passed is the one setup.

    :param obj: obj to bake sim to
    :param time_range: time range to bake on
    :return: True/False
    '''
    if not obj or not maya.cmds.objExists(PARTICLE_DEFAULT_NAME):
        return False
    start_frame, end_frame = time_range or [ maya.cmds.playbackOptions(minTime=True, query=True), maya.cmds.playbackOptions(maxTime=True, query=True)]

    maya.cmds.bakeResults('physics_locator', t=(start_frame, end_frame), simulation=True)
    maya.cmds.delete(['original_animation_locator', PARTICLE_DEFAULT_NAME])
    maya.cmds.bakeResults(obj, t=(start_frame,end_frame))
    maya.cmds.delete(['physics_locator', 'physics_point_const'])

    return True

if __name__ != '__main__':
    obj_list = maya.cmds.ls(sl=True)
    if obj_list:
        obj = obj_list[0]
        setup_spring(obj, spring_weight=0.5) # Set spring value here
        bake_spring(obj)

Want to run straight in the script editor in maya? Change line 60:
if __name__ != '__main__':
to
if __name__ == '__main__':