Dynamic operator description

Creating an operator in the Blender Python API, its description is usually specified in its “bl_description” parameter. However, quite often the same operator performs different actions in different cases, and a constant description does not describe all its capabilities. In this case, a dynamic description can be given to an operator.

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To assign a dynamic description to an operator, we can use the “description” class method.

@classmethod
def description(cls, context, properties):

1 2	@classmethod def description(cls, context, properties):

Method parameters:

cls – self class pointer

context – pointer to the executing context

properties – with this property, we can access the input parameters of the operator

The return value of the method will be displayed as a description of the operator.

For example, to have one description for the operator when the mesh is in the Edit mode and another – for the Object mode, let’s define simple condition in the “description” method:

@classmethod
def description(cls, context, properties):
    if context.mode == 'OBJECT':
        return 'DESCRIPTION FOR OBJECT MODE'
    elif context.mode == 'EDIT_MESH':
        return 'DESCRIPTION FOR EDIT MODE'

@classmethod

def description(cls, context, properties):

if context.mode == 'OBJECT':

return 'DESCRIPTION FOR OBJECT MODE'

elif context.mode == 'EDIT_MESH':

return 'DESCRIPTION FOR EDIT MODE'

If the operator has input parameters, for example, “param”, and depending on its value, the description of the operator also changes, let’s write the following condition in the “description” method:

@classmethod
def description(cls, context, properties):
    if properties.param != '':
        return 'DESCRIPTION BY PARAMETER'

@classmethod

def description(cls, context, properties):

if properties.param != '':

return 'DESCRIPTION BY PARAMETER'

The operator input parameters are accessed through the “properties”.

Full code for operator with dynamic description:

class TEST_OT_test_op(Operator):
    bl_idname = 'test.test_op'
    bl_label = 'Test'
    bl_description = 'Default Description'
    bl_options = {'REGISTER'}

    param: StringProperty(
        name='param',
        default=''
    )

    @classmethod
    def description(cls, context, properties):
        if properties.param != '':
            return 'DESCRIPTION BY PARAMETER'
        elif context.mode == 'OBJECT':
            return 'DESCRIPTION FOR OBJECT MODE'
        elif context.mode == 'EDIT_MESH':
            return 'DESCRIPTION FOR EDIT MODE'

    def execute(self, context):
        return {'FINISHED'}

class TEST_OT_test_op(Operator):

bl_idname = 'test.test_op'

bl_label = 'Test'

bl_description = 'Default Description'

bl_options = {'REGISTER'}

param: StringProperty(

name='param',

default=''

)

@classmethod

def description(cls, context, properties):

if properties.param != '':

return 'DESCRIPTION BY PARAMETER'

elif context.mode == 'OBJECT':

return 'DESCRIPTION FOR OBJECT MODE'

elif context.mode == 'EDIT_MESH':

return 'DESCRIPTION FOR EDIT MODE'

def execute(self, context):

return {'FINISHED'}