Reference/Release Notes/2.81/Python API

Blender 2.81: Python API

Python Upgrade

Python has been upgraded from 3.7.0 to version, 3.7.4.

API Changes

  • IDMaterials.clear() and IDMaterials.pop() no longer have an update_data parameter. It now always behave as if update_data=True was passed. (c70f975d5c3b961e0c)
  • Bone.use_inherit_scale and EditBone.use_inherit_scale are deprecated in favor of the new inherit_scale enum property. (fcf2a712)
  • CopyRotationConstraint.use_offset is deprecated in favor of the new mix_mode enum. (f4056e9e)
  • CyclesShaderWrapper has been removed developers should be using PrincipledBSDFWrapper now. (rBA19819fb1ce7e)
  • ShaderNodeMapping was rewritten to have dynamic inputs, so direct access to translation, rotation and scale has been removed and is now done via inputs['Location'], inputs['Rotation'] and inputs['Scale']. Also min/max was removed entirely and should be replaced by access to the Extension parameter of the Texture node ([1], [2])
  • Bone properties related to its position and orientation have been marked read only, because modifying them was never expected by the code and resulted in inconsistent state. The rest pose should only be modified through EditBone. (d4f8bc80)

Mesh Replacement

Meshes can now be cleared of all geometry by calling mesh.clear_geometry() (6d2f9b1dfa98). This allows the reuse of existing mesh datablocks, by clearing with mesh.clear_geometry() and subsequently recreating with, for example, mesh.from_pydata(). Not only is it faster than creating a new mesh and swapping out the old one, but this also makes it easier for exporters to understand this actually represents the same logical mesh (instead of exporting a different static mesh for every frame).

Shape keys are not freed by this function. Freeing those would require tagging the depsgraph for relations update, which is an expensive operation. They should be removed explicitly if necessary.

Material slots are also not cleared by this function, in the same way that they are not cleared when manually removing all geometry from a mesh.


  • Support for displaying node sockets with square and diamond shapes, using the new NodeSocket.display_shape property. (2ba233a)


  • Constraint collections of objects and bones now have a move() method for reordering the stack. (36e23c95)
  • The length property of bones is now implemented in C and available for use in drivers and UI. (d4f8bc80)


Shadow map refactor removed some properties from the API. (d8aaf25c23fa)

  • shadow_buffer_soft, shadow_buffer_exp, shadow_buffer_bleed_bias and contact_shadow_soft_size have been removed for all light data types.
  • SunLight.shadow_buffer_clip_start and SunLight.shadow_buffer_clip_end have been removed due to sunlight now having auto clip distances.
  • SceneEEVEE.use_sss_separate_albedo and SceneEEVEE.shadow_method have also been removed.


Operators can now have a dynamic tooltip that changes based on the context and operator parameters. (9ecbd67d)

With an operator defined as (irrelevant parts omitted):

class WM_OT_tooltip_test(bpy.types.Operator):
    arg: bpy.props.StringProperty()

    def description(cls, context, properties):
        return "Arg is: " + properties.arg

The following button would have a tooltip that says "Arg is: FOO".

layout.operator('wm.tooltip_test').arg = 'FOO'

This is mainly intended for cases when multiple similar but distinct operations are implemented for technical reasons as one operator with a mode switch parameter.


The depsgraph_update_post and frame_change_post handlers are now receiving an optional depsgraph argument which allows to access evaluated datablocks within corresponding dependency graph. This can be used, for example, to alter scene prior it gets rendered.

The new function signatures are:

def depsgraph_update_post_handler(scene, depsgraph):

def frame_change_post_handler(scene, depsgraph):

NOTE: The depsgraph argument is optional and can be left out. This keeps compatibility with existing scripts.

Details about access of evaluated datablocks can be found in the API documentation.