Efficient way to get selected vertices via python (without iterating over the entire mesh)

Question

What's the best/fastest way to construct a list of selected vertices for a mesh object in python?

I want to avoid iterating over every vertex in the mesh if possible, since that seems like a really inefficient/wasteful way to go about it.

There's a nice attribute called select_history in the bmesh module that gives you a list of vertices in the order that they were selected...but of course, it will only give you verts that have been selected manually (not by box or circle select) after the bmesh was initialized.

I've been searching through the edit mesh api for an attribute that will give me an updated list of selected verts (so that I don't have to iterate over the whole mesh). Does such a thing not exist?

Answer 1

You have to iterate over the entire mesh since blender isn't storing this data in a separate list internally.

You can use the following line of code to get a list if selected vertices from a bpy.types.Mesh object ('mesh' in the code):

selected_verts = list(filter(lambda v: v.select, mesh.vertices))

or with list comprehension:

selected_verts = [v for v in mesh.vertices if v.select]

However, in most cases, brute force looping through all the vertices of the mesh should be fine.

Answer 2

Just building on Gwenn's great answer,

• If you are in Edit Mode, all the vertices may appear selected. Switch to Object Mode so the vertex selection gets updated.
• You can directly access the vertices from active_object.data, without looking for the mesh in bpy.data.meshes

Code:

mode = bpy.context.active_object.mode
# we need to switch from Edit mode to Object mode so the selection gets updated
bpy.ops.object.mode_set(mode='OBJECT')
selectedVerts = [v for v in bpy.context.active_object.data.vertices if v.select]
for v in selectedVerts:
    print(v.co)
# back to whatever mode we were in
bpy.ops.object.mode_set(mode=mode)

Note that you can use the same logic to find selected edges,

selectedEdges = [e for e in bpy.context.active_object.data.edges if e.select]

Answer 3

import bpy
import numpy as np

ob = bpy.context.object
count = len(ob.data.vertices)
sel = np.zeros(count, dtype=bool)

ob.data.vertices.foreach_get('select', sel)

print(sel)

# super fast. No looping

The foreach_get and foreach_set methods are a fast way to get at certain collection properties in blender. They can be thousands of times faster than looping and hundreds of times faster than list comprehension. The code above returns a bool array. If you continue to work with numpy arrays in your code you can index subsets of your arrays with the bool array.

x = np.array([0, 0, 1, 0, 1], dtype=bool) 
y = np.array([1, 2, 3, 4, 5]) 
print(y[x]) 

>>> (numpy array([3, 4]))

Answer 4

In newer versions of Blender you can use (while in Edit Mode):

bpy.context.active_object.data.total_vert_sel
bpy.context.active_object.data.total_edge_sel
bpy.context.active_object.data.total_face_sel

See: https://docs.blender.org/api/current/bpy.types.Mesh.html?highlight=_sel#bpy.types.Mesh.total_edge_sel

Also count_selected_items() returns the number of selected items (vert, edge, face):

bpy.context.active_object.data.count_selected_items()

To programmatically switch to Edit Mode call: bpy.ops.object.mode_set(mode="EDIT”)

Answer 5

Edit mode bmesh & numpy

Thought I'd throw this one in the ring as an example to speed up getting selection purely from an edit mode bmesh.

For example sake, will take a test run via entering code in python console. The default cube "Cube" is active object.

Load in an edit mode bmesh from the mesh of the current edit object.

>>> import bmesh    
>>> bm = bmesh.from_edit_mesh(C.edit_object.data)

Create a numpy verts array

>>> import numpy as np
>>> verts = np.array(bm.verts)
>>> verts
array([<BMVert(0x7f8ac738e090), index=0>,
       <BMVert(0x7f8ac738e0c8), index=1>,
       <BMVert(0x7f8ac738e100), index=2>,
       <BMVert(0x7f8ac738e138), index=3>,
       <BMVert(0x7f8ac738e170), index=4>,
       <BMVert(0x7f8ac738e1a8), index=5>,
       <BMVert(0x7f8ac738e1e0), index=6>,
       <BMVert(0x7f8ac738e218), index=7>], dtype=object)

Define a "foreach get" method

Example of np.frompyfunc as suggested in this stackoverflow answer

frompyfunc iterates as the [a for a in A.flat] does, but is somewhat faster, and throws all the power of numpy broadcasting at the task.

>>> selected = np.frompyfunc(lambda a: a.select, 1, 1)

With all verts selected

>>> selected(verts)
array([True, True, True, True, True, True, True, True], dtype=object)

Change selection in UI to single vert, run again

>>> selected(verts)
array([False, False, False, False, False, True, False, False],
      dtype=object)

Cannot index with the object dtype

>>> sel = selected(verts).astype(bool)
>>> sel
array([False, False, False, False, False,  True, False, False])

>>> verts[sel]
array([<BMVert(0x7f8ac738e1a8), index=5>], dtype=object)

Above could be used to create a function, "get_where" that takes the sequence, the property name and value to check, and the property to return

selected_verts = get_where(bm.verts, "select", True, "index")

returning an array of indices of selected vertices.

Answer 6

Related to the numpy approach which is super fast to get a count - the issue for me was - now that I have a count - how do I quickly get which vertex it is without loops:

    vert_count = len(obj.data.vertices)
    sel = np.zeros(vert_count, dtype=np.bool)
    obj.data.vertices.foreach_get('select', sel)
    sel_count = np.count_nonzero(sel)

    # get the actual vertices that are selected
    nv = np.array(obj.data.vertices)
    sel_vert_list = nv[sel]

Answer 7

Since Blender 2.8, multi-object editing makes the previously given answers insufficient, as they don't list the selected vertices of non active objects.

The following snippet solves this issue by creating a dictionary with the paths of the edited objects as keys and the indices of their respective selected vertices as key values :

import bpy
import bmesh

dic_v = {}
for o in bpy.context.objects_in_mode:
    dic_v.update( {o : []} )
    bm = bmesh.from_edit_mesh(o.data)
    for v in bm.verts:
        if v.select:
            dic_v[o].append(v.index)

print(dic_v)

Answer 8

problem concerning this subject, using blender v2.78

v.select value of v in bpy.context.active_object.data.vertices seems ALWAYS True:

• I go in 3D View, select a mesh, go in edit mode: all vertices appear selected
• I run below described script : all v.select values appear True
• I manually do a deselect all vertices (pressing A in 3D View, Edit mode)
• I run the script again : All v.select values remain True!

script does this:

for v in bpy.context.active_object.data.vertices:
    print(str(v.select))

More completely:

I'm using a custom operator to perform this, which assures Edit mode as needed state and allows a shortkey setup to call the operator :

class stitch(bpy.types.Operator):
    bl_idname = "my.printselectedstates"  
    bl_label = "printselectedstates"  

    @classmethod  
    def poll(cls, context):  
        ob = context.active_object  
        return ob is not None and ob.mode == 'EDIT' 

    def execute(self, context):  
        for v in context.active_object.data.vertices:
            print(str(v.index) + ' ' + str(v.select)) 
        return {'FINISHED'} 

Answer 9

print index of selected vertex with order

import bpy
import bmesh

obj = bpy.context.object

data = obj.data
bm = bmesh.from_edit_mesh(data)

v = [s.index for s in bm.select_history if isinstance(s, bmesh.types.BMVert)]
print(v)