select_keyed.py

import pymel.core as pm
   
def select_keyed_objs():
    # empty list for our keyed objects to go in
    keyed_objects = []
    # loop over all objects in the scene (transform as mask to ignore animcurves etc)
    for obj in pm.ls(type='transform'):
        # check the keyframe count on the object
        if pm.keyframe(obj, query=True, keyframeCount=True):
            # if it's keyed, append it to our list
            keyed_objects.append(obj)
    return keyed_objects
    
# usage
'''
import pymel.core as pm
pm.select(select_keyed_objs(), replace=True)