Python • Page 30 of 33 • B3D

How to check if Blender object property/attribute is read-only

Leave a Comment / Blender 3D / Nikita / 14.12.2018

To check is an attribute/property of any Blender object (mesh, node, modifier, etc.) read-only:

With the is_property_readonly function, execute the following command:

<object> .is_property_readonly (‘<property name>’)

Through the rna structure, execute the following command:

<object> .bl_rna.properties [‘<property name>’]. is_readonly

For example, for the “is_editmode” mesh property (is the mesh in edit mode or not):

bpy.context.active_object.data.is_property_readonly('is_editmode')

# True


bpy.context.active_object.data.bl_rna.properties['is_editmode'].is_readonly

# True

bpy.context.active_object.data.is_property_readonly('is_editmode')

# True

bpy.context.active_object.data.bl_rna.properties['is_editmode'].is_readonly

# True

How to get the version of the add-on installed in Blender

Leave a Comment / Blender 3D / Nikita / 12.11.2018

A complete list of add-ons installed in Blender we can get using the addon_utils:

import addon_utils
print(addon_utils.modules()[:])

# <module 'space_view3d_3d_navigation' from ...

import addon_utils

print(addon_utils.modules()[:])

# <module 'space_view3d_3d_navigation' from ...

Having the add-ons list, we can get the version of the desired add-on by its name with the following code:

import addon_utils
print([addon.bl_info.get('version', (-1,-1,-1)) for addon in addon_utils.modules() if addon.bl_info['name'] == 'ADD-ON_NAME'][0])

# (1,4,0)

import addon_utils

print([addon.bl_info.get('version', (-1,-1,-1)) for addon in addon_utils.modules() if addon.bl_info['name'] == 'ADD-ON_NAME'][0])

# (1,4,0)

Where the ADD-ON_NAME is the name of the desired add-on.

If the add-on is missing a version indication, the default result will be returned.

# (-1,-1,-1)

1	# (-1,-1,-1)

How to programmatically switch between vertex, edge and face selection mode

Leave a Comment / Blender 3D / Nikita / 03.11.2018

Change the mesh_select_mode property to switch in mesh edit mode between vertex, edge and polygon selection mode in Blender.

For vertex selection mode:

bpy.context.tool_settings.mesh_select_mode = (True, False, False)

1	bpy.context.tool_settings.mesh_select_mode = (True, False, False)

Edge selection mode:

bpy.context.tool_settings.mesh_select_mode = (False, True, False)

1	bpy.context.tool_settings.mesh_select_mode = (False, True, False)

And face selection mode:

bpy.context.tool_settings.mesh_select_mode = (False, False, True)

1	bpy.context.tool_settings.mesh_select_mode = (False, False, True)

The multi-select mode is enabled too. For example for vertex and face selection mode:

bpy.context.tool_settings.mesh_select_mode = (True, False, True)

1	bpy.context.tool_settings.mesh_select_mode = (True, False, True)

In BMesh for vertex, edge and face selection mode:

bm.select_mode = {'VERT'}
bm.select_mode = {'EDGE'}
bm.select_mode = {'FACE'}

bm.select_mode = {'VERT'}

bm.select_mode = {'EDGE'}

bm.select_mode = {'FACE'}

For multi-select in BMesh:

bm.select_mode = {'VERT', 'EDGE', 'FACE'}

1	bm.select_mode = {'VERT', 'EDGE', 'FACE'}

Learning loops

1 Comment / Blender 3D / Nikita / 26.06.2018

In general, the “loop” is usually a sequential selection of several points, edges or polygons of a mesh.

However, there is an element in the mesh structure, which is also called a “loop”. It is a combination of one vertex with one edge of the mesh. Let’s try to learn what these “loops” are for.

Learning loopsRead More »

How to pass command line arguments to a Blender python script or add-on

Leave a Comment / Blender 3D / Nikita / 17.04.2018

When starting Blender from the console it processes all parameters passed through the command line. However, some scripts and add-ons for proper work may require specifying their unique command line arguments. If you specify such additional parameters in the command line, Blender will also try to process them, which is likely to result in an error. Blender provides a special way to exclude such arguments from own processing.

How to pass command line arguments to a Blender python script or add-onRead More »

Creating radio buttons in the Blender add-ons interface

3 Comments / Blender 3D / Nikita / 09.02.2018

State switches so-called “radio buttons” are used in the case to limit the choice by one value from several available ones. There are a lot of such buttons in the Blender interface, for example, switching between RGB and BW rendering modes or setting the texture mapping mode. Such buttons can be created in the Blender add-ons interface too.

Let’s create our own radio button switcher.

Creating radio buttons in the Blender add-ons interfaceRead More »

How to programmatically check if the operator is registered in Blender API

Leave a Comment / Blender 3D / Nikita / 25.12.2017

Single add-on or script can contain several different operators, and not all of them may be registered in the API by the register() function. To verify that the required operator is registered in the Blender API, run the following command:

hasattr(bpy.types, bpy.ops._operator_bl_idname_.idname())

1	hasattr(bpy.types, bpy.ops._operator_bl_idname_.idname())

Where:

_operator_bl_idname_ – the text value of the bl_idname operator property.

For example for an operator:

class TestOperator(bpy.types.Operator):
    bl_idname = 'test.operator'
    bl_label = 'Test operator'

    def execute(self, context):
        pass

class TestOperator(bpy.types.Operator):

bl_idname = 'test.operator'

bl_label = 'Test operator'

def execute(self, context):

pass

the command will look like this:

hasattr(bpy.types, bpy.ops.test.operator.idname())

1	hasattr(bpy.types, bpy.ops.test.operator.idname())

How to programmatically check if the Blender add-on is registered

Leave a Comment / Blender 3D / Nikita / 25.12.2017

To start working every Blender add-on must be registered by setting up the checkbox before add-on name in the User Preferences window – Add-ons page.

To programmatically find out if the required add-on is registered, run the following command:

'add-on_name' in the file bpy.context.user_preferences.addons

1	'add-on_name' in the file bpy.context.user_preferences.addons

Where:

add-on_name – the name of the add-on file (without the .py extension) or the name of the add-on package, if it was installed from the package.

Debugging multifile Blender add-on by quick reinstall

Leave a Comment / Blender 3D / Nikita / 17.11.2017

It is convenient to use the following system for debugging developing multi-file Blender add-ons. But it has one drawback: modules imported in __init__.py file becomes available only after the file running (after the execution of the register() function). This means that any access to the imported modules before they are registered will cause an error. This is not critical in most cases, but it will cause a problem if, for example, in one imported module is used inheritance from the class, described in the other imported module, because the classes descriptions are processed before the add-on registration.

To get more freedom working with imported modules, we can use another way to debug the add-on – do not run the add-on directly from the development directory, but install it in Blender and check its “live” work. However, manual add-on reinstallation requires a set of routine actions, which complicates such sort of debugging. This issue can be solved by reinstalling the add-on in automatic mode.

Debugging multifile Blender add-on by quick reinstallRead More »

How to install and uninstall Blender add-on via python API

Leave a Comment / Blender 3D / Nikita / 16.11.2017

Blender add-ons installation and uninstallation can be managed through the python API. Use the following commands in a script:

To deactivate the add-on:

bpy.ops.wm.addon_disable(module = 'add-on name')

1	bpy.ops.wm.addon_disable(module = 'add-on name')

To uninstall the add-on:

bpy.ops.wm.addon_remove(module = 'add-on name')

1	bpy.ops.wm.addon_remove(module = 'add-on name')

How to install and uninstall Blender add-on via python APIRead More »