#https://blender.stackexchange.com/questions/82144/how-can-i-call-and-edit-animation-keys-from-the-dope-sheet-in-python

import bpy

def reverse_kps(keyframe_points, frame_start, frame_end):
    rval = []

    for i in range(len(keyframe_points)):
        kp = keyframe_points[i]
        copy = {}

        copy["handle_left"] = temporally_reversed(kp.handle_right, frame_start, frame_end)
        copy["handle_left_type"] = kp.handle_right_type
        copy["handle_right"] = temporally_reversed(kp.handle_left, frame_start, frame_end)
        copy["handle_right_type"] = kp.handle_left_type
        copy['co'] = temporally_reversed(kp.co, frame_start, frame_end)
        if (i>0):
            copy["interpolation"] = keyframe_points[i-1].interpolation
            copy["easing"] = keyframe_points[i-1].easing

        rval.insert(0, copy)

    return rval


def temporally_reversed(fry, frame_start, frame_end):
    fr2 = frame_end - (fry[0] - frame_start)
    c2 = (fr2, fry[1])
    return c2


def overwrite(dst, src):
    for i in range(len(src)):
        for attr in src[i].keys():
            setattr(dst[i], attr, src[i][attr])


def reverse_keyframes(action):

    action_start = None
    action_end = None
    for fc in action.fcurves:
        kp0 = fc.keyframe_points[0]
        if action_start is None or action_start > kp0.co[0]:
            action_start = kp0.co[0]
        kp9 = fc.keyframe_points[-1]
        if action_end is None or action_end > kp9.co[0]:
            action_end = kp9.co[0]

    for fc in action.fcurves:
        reversed_kp = reverse_kps(fc.keyframe_points, action_start, action_end)
        overwrite(fc.keyframe_points, reversed_kp)

def reverse_keyframes_o(obj):
    reverse_keyframes(obj.animation_data.action)

#
#
#

reverse_keyframes_o(bpy.context.active_object)