Why isn't my 'frame_change' app handler working?

Question

I am new to scripting in Blender and I am having trouble attaching an app handler to keyframe changes during an animation.

Below is my Python code:

import bpy

def my_handler():
    bpy.data.objects["Cube"].location[0] += 0.5

bpy.app.handlers.frame_change_pre.append(my_handler)

I tried to call my_handler, which moves an object when the frame changes, manually or when the animation starts.

I have written the code in text editor. After I run script, nothing really happens. Please help me someone out there I couldn't find anything online.

Answer 1

As we can see in the documentation at https://docs.blender.org/api/current/bpy.app.handlers.html :

import bpy
from bpy.app.handlers import persistent

@persistent
def load_handler(dummy):
    print("Load Handler:", bpy.data.filepath)

bpy.app.handlers.load_post.append(load_handler)

handlers need an argument.

You probably do not need it persistent, but you need the dummy part. This will work:

import bpy

def my_handler(dummy):
    bpy.data.objects["Cube"].location[0] += 0.5

bpy.app.handlers.frame_change_pre.append(my_handler)