How to block custom properties from being edited by the user?

Question

I'm creating a custom property for each object in my scene but don't want the user to be able to edit it. Is it possible to block the property in ui ? Here is my code :

import bpy

allObjects = list(bpy.data.objects)

for element in allObjects:
    element["myProp"] = "My value"

Answer 1

You might create a custom property and pass only a get method:

import bpy

#default getter
def get_my_prop(self):
    return self['my_prop']

#omit the setter with a given getter to make it read-only
bpy.types.Object.my_prop = bpy.props.StringProperty(get=get_my_prop)

for obj in bpy.context.selected_objects:
    #assign the value directly
    obj['my_prop'] = "My Value"

It looks like this in the properties panel in blender 2.71:

Answer 2

I was not satisifed with the way the field is dimmed and the value can't be accessed in a color field when it is read-only.

I added custom get and set methods to ensure the user can't modify it from the interface, while being able to click the field and copy the values inside the RGB widget.

import bpy


bpy.types.Object.my_prop = bpy.props.FloatVectorProperty(
    subtype="COLOR", 
    set=lambda s, c: None, 
    get=lambda s: s["my_prop"], 
    min=0, 
    max=1
)


for obj in bpy.data.objects:
    obj["my_prop"] = (0.5, 0.3, 0.2)

You can still change the property with a custom Hex value using the interface, but I guess this is managed differently so I don't know how to prevent that. You can also change the HSV sliders but the changes will be discarded when you exit the widget.