I have to move an object (cube, camera, ...) according to a value from a industrial plc. In principle that works fine - but after a short while Blender (2.80) stops working. I saw, that the Windows Taskmanager shows a continiously increasing number of handles, the nuber of Threads is nearly constant. Do i have to dispose or kill anything? I can't find any hint :-(
Any comments welcome and many thanks in advance!

    import bpy, time, threading
    def moveObj(val): # reduced to make it easier to understand
        val = val + 0.05
        if val > 20:

       bpy.data.objects['MyObject'].location=(val, -val, val*0.5)
       threading.Timer(0.05, moveObj, [val]).start()

    moveObj(2) #call the method with start-value


  • 1
    $\begingroup$ For every call to moveObj you're creating a thread that in itself runs moveObj again. You've got an infinite recursion. Use a modal operator with a timer instead in order to execute a function every x seconds. $\endgroup$ – Robert Gützkow Oct 9 '19 at 18:16
  • 1
    $\begingroup$ @Petra Welcome to Blender.SE. What does "plc" in the title mean? $\endgroup$ – Leander Oct 9 '19 at 18:52
  • $\begingroup$ Many, many thanks for all your comments! @rjg: i'm trying at the moment, it seems to work well! I will post the result! $\endgroup$ – Petra Berlina Oct 10 '19 at 8:50
  • $\begingroup$ @leander: plc means programmable logic controller - you can find these these devices in every switching cubical link $\endgroup$ – Petra Berlina Oct 10 '19 at 8:50

Your code performs infinite recursions. For every call to moveObj you're creating a thread that in itself calls moveObj again. A solution for your goal is to use a modal operator in combination with a timer to execute a function every x seconds. An example for this can be found in operator_modal_timer.py

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many thanks for your hints - this is my current solution. It works but of course it's less then ideal (using global variables, ...) Anyhow, maybe somebody can use parts of it - and also of course - comments are very welcome! Cheers Petra

import bpy
from bpy.utils import register_class, unregister_class

xTimer = None
enable = False

class ModalTimer(bpy.types.Operator):
    bl_idname = "plc.modal_timer_operator"
    bl_label = "timer"
    val = 0

    def modal(self, context, event):
        if event.type == 'TIMER' and enable == True:
            self.val += 0.5
            if self.val > 20: 
            print("trigger, new Value: ", self.val)
            bpy.data.objects['MyObject'].location=(self.val, -self.val, self.val*0.5)
        return {'PASS_THROUGH'}            

    def execute(self, context):
        global xTimer
        if enable == True:
            if xTimer == None:
                # Add a modal handler to the window manager, for the given modal operator (called by invoke() with self, 
                # just before returning {‘RUNNING_MODAL’})
            xTimer = context.window_manager.event_timer_add(0.1, window=context.window)
            if xTimer != None:
        return {'RUNNING_MODAL'}

class PanelPlc(bpy.types.Panel):
    bl_label = "plc handling"
    bl_category = "programable logic controller"
    bl_space_type = "VIEW_3D"
    bl_region_type = "UI"
    bl_idname = "PLC_PT_panel"

    def draw(self, context):
        layout = self.layout
        col = layout.column(align=True)
        row = col.row(align=True)
        row.operator("plc.enable", text='use plc values')
        row = self.layout.row()
        row.operator("plc.disable", text='stop using plc values')

class Button(bpy.types.Operator):
    """enable the plc to refresh parameters"""  # tooltip 
    bl_idname = "plc.enable"
    bl_label = "enable plc"

    def execute(self, context):
        global enable
        enable = True

class ButtonStop(bpy.types.Operator):
    """disable plc access"""    # tooltip 
    bl_idname = "plc.disable"
    bl_label = "disable plc"

    def execute(self, context):
        global enable
        enable = False

def register():

def unregister():

if __name__ == "__main__": 

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