I wrote a script that imports and modifys two objects. It works as following: The script imports an .obj and makes some modifactions. The position of the object stays the same. After the modifications, the same .obj is imported again. Then the last imported object is selected and Boolean/Difference/Object1 used.

The Boolean works without problems, when I run the script till the object is imported again and I select the this object by hand and do the Bool.

The script runs till bpy.context.object.modifiers["Boolean"].object = bpy.data.objects[NameWOFormat].

I understand that I have a problem with my selection. There is a small Modifier symbol next to the Name "Object1" in the Outliner Window. If it would run as it should, the symbol would be behind "Object1.001". That's the reason I think it's a selection problem.

Am I using the wrong command for the selection?

import bpy
import os
import bmesh
from pathlib import Path
from mathutils import Vector, kdtree, Matrix

NameWOFormat ="Object1"

# Modifier Boolean
def ModDif():
    global NameWoFormat
    global NameSubstrObject
    bpy.context.object.modifiers["Boolean"].operation = 'DIFFERENCE'
    bpy.context.object.modifiers["Boolean"].object = bpy.data.objects[NameWOFormat]
    bpy.ops.object.modifier_apply(apply_as='DATA', modifier="Boolean")


# Now I do some modifications on Object1. I save this block of code here.

# Change into Object-Mode

# Import Object1 again and use Boolean
NameSubstrObject = NameWOFormat + ".001"

# Do Boolean edit
bpy.data.objects[NameSubstrObject].select = True
  • $\begingroup$ Can you post a screenshot of your modifier panel after running this script? $\endgroup$
    – Rick Riggs
    Aug 29, 2016 at 14:54
  • $\begingroup$ i.imgur.com/De7FdP2.jpg $\endgroup$
    – Anokino
    Aug 29, 2016 at 15:16

2 Answers 2


You can add modifiers without using operators or relying on what is selected.

import bpy

# this creates Object1
# this creates Object1.001

obj = bpy.data.objects['Object1.001']
m = obj.modifiers.new(name='cutting modified obj',type='BOOLEAN')
m.object = bpy.data.objects['Object1']
m.operation = 'INTERSECT'
  • $\begingroup$ This works for me. Thank you. One more question: When the Boolean prints the Error "Cannot execute boolean operation", is there a log where i can find out what the problem is? $\endgroup$
    – Anokino
    Aug 30, 2016 at 12:34
  • 1
    $\begingroup$ @Anokino you have to run blender in terminal/command line, script output and errors will be printed there. $\endgroup$
    – Noidea
    Aug 30, 2016 at 13:15

Operator is applied to the active object. There is always one active object in a scene, so deselect doesn't clear it and Object1 stays active. Although active object is the last selected object, call to select doesn't affect it.

You need to either set active object:

bpy.context.scene.objects.active =  bpy.data.objects[NameSubstrObject]

or create a global variable

myObject = bpy.data.objects[NameSubstrObject]

and use it instead of bpy.ops.object


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