Dynamically add properties to PropertyGroup Class

Question

How can I dynamically add or remove properties in a class like this? I want to make a user interface where you can click on a button that will add new options and properties in that same user interface but for that I need a way to append new settings into this class.

import bpy

class MyPropertyGroup(bpy.types.PropertyGroup):
    custom_1: bpy.props.FloatProperty(name="My Float")
    custom_2: bpy.props.IntProperty(name="My Int")


bpy.utils.register_class(MyPropertyGroup)

bpy.types.Object.my_prop_grp = bpy.props.PointerProperty(type=MyPropertyGroup)


# test this worked
bpy.data.objects[0].my_prop_grp.custom_1 = 22.0

So how would I add a custom_3 property to this class for example?

Answer 1

custom_2: bpy.props.IntProperty(name="My Int") is a class property with a type annotation. I don't know what Voodoo Blender uses behind the scenes, but it seems to use that annotation.

This seems to be what you were looking for:

MyPropertyGroup.__annotations__['custom_3'] = bpy.props.FloatProperty(name="The Latter")

Or you could obviously just subclass the group and use that instead

class MyPropertySubGroup(MyPropertyGroup):
   custom_3: bpy.props.IntProperty(name="The Latter")

bpy.utils.register_class(MyPropertySubGroup)
bpy.types.Object.my_prop_grp = bpy.props.PointerProperty(type=MyPropertySubGroup)

or you can subclass it more dynamically, again using annotations

MyPropertySubGroup = type('MyPropertySubGroup', (MyPropertyGroup,), {
    '__annotations__': {'custom_3': bpy.props.FloatProperty(name="The Latter")},
})
bpy.utils.register_class(MyPropertySubGroup)
bpy.types.Object.my_prop_grp = bpy.props.PointerProperty(type=MyPropertySubGroup)