<!-- GENERATED by tools/generators/examplesDocsEmitter.py from python/ - do not edit -->
(testmodels-deleteitemstest)=
# deleteItemsTest.py

You can view and download this file on Github: [deleteItemsTest.py](https://github.com/jgerstmayr/EXUDYN/tree/master/python/TestModels/deleteItemsTest.py)

```{code-block} python
:linenos:

#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
# This is an EXUDYN example
#
# Details:  Test for deleting items; we make a chain of 3 mass points and remove the first mass point
#
# Author:   Johannes Gerstmayr
# Date:     2025-05-08
#
# Copyright:This file is part of Exudyn. Exudyn is free software. You can redistribute it and/or modify it under the terms of the Exudyn license. See 'LICENSE.txt' for more details.
#
#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

import exudyn as exu
from exudyn.utilities import *
import exudyn.graphics as graphics 
import numpy as np

testIsActive = exu.sys.get('testIsActive', False)


SC = exu.SystemContainer()
mbs = SC.AddSystem()

oGround = mbs.CreateGround()

nMasses=3
mass=0.5
length=0.25
gravity=9.81
initialVelocity=0.5

createMassDicts = []
nodeNumbers = []
bodyNumbers = []
loadNumbers = []
jointNumbers = []
sensorNumbers = []
lastBody = oGround
for i in range(nMasses):
    oDict = mbs.CreateMassPoint(referencePosition=[length*(i+1),0,0],
                                initialVelocity=[0,-initialVelocity,0],
                                mass=mass,
                                gravity=[0,-gravity,0],
                                returnDict=True)
    oMass = oDict['bodyNumber']
    createMassDicts.append(oDict)
    bodyNumbers.append(oDict['bodyNumber'])
    nodeNumbers.append(oDict['nodeNumber'])
    loadNumbers.append(oDict['loadNumber'])

    oJoint = mbs.CreateDistanceConstraint(itemNumbers=[lastBody,oMass])
    jointNumbers.append(oJoint)
    lastBody = oMass

    #add sensors:
    sPos = mbs.AddSensor(SensorBody(bodyNumber=lastBody, storeInternal=True,
                                    outputVariableType=exu.OutputVariableType.Position))
    sensorNumbers.append(sPos)

#for debugging, look at this output:
# mbs.systemData.Info()

#for test cases we delete some connectors and mass point
# exu.Print('*******************************************\n')
delID0 = 0
delID1 = 1

exu.Print('delete object:',jointNumbers[delID0])
mbs.DeleteObject(jointNumbers[delID0],suppressWarnings=False) #incl. markers
#delete also the second joint
exu.Print('delete object:',jointNumbers[delID1]-1)
mbs.DeleteObject(jointNumbers[delID1]-1,suppressWarnings=False) #incl. markers


exu.Print('delete sensor:',sensorNumbers[delID0])
mbs.DeleteSensor(sensorNumbers[delID0],suppressWarnings=False)

exu.Print('delete load:',loadNumbers[delID0])
mbs.DeleteLoad(loadNumbers[delID0],suppressWarnings=False) #incl. marker
exu.Print('delete object:',bodyNumbers[delID0])
mbs.DeleteObject(bodyNumbers[delID0],suppressWarnings=False) #incl. markers

#for debugging, look at this output:
# exu.Print('*******************************************\n')
# mbs.systemData.Info()

#now add constraint again ... delID0 is now the new body; would be easier if names are used
oJoint = mbs.CreateDistanceConstraint(itemNumbers=[oGround,bodyNumbers[delID0]])

#%%
mbs.Assemble()

tEnd = 0.5
stepSize = 0.002

simulationSettings = exu.SimulationSettings()
simulationSettings.timeIntegration.newton.useModifiedNewton = False #Just for the test; modified Newton is usually faster
#simulationSettings.solution.file.writePeriod = 1e-1
simulationSettings.solution.sensors.writePeriod = 1e-2
simulationSettings.timeIntegration.numberOfSteps = int(tEnd/stepSize) #must be integer
simulationSettings.timeIntegration.endTime = tEnd
simulationSettings.timeIntegration.verboseMode = 1

SC.visualizationSettings.nodes.drawNodesAsPoint=False
SC.visualizationSettings.nodes.defaultSize=0.05
SC.visualizationSettings.nodes.tiling = 8

if not testIsActive:
    SC.renderer.Start()
    SC.renderer.DoIdleTasks()

mbs.SolveDynamic(simulationSettings)

if not testIsActive:
    SC.renderer.DoIdleTasks()
    SC.renderer.Stop()

#+++++++++++++++++++++++++++++++++++++++++++++
uTotal = sum(mbs.GetSensorValues(mbs.systemData.NumberOfSensors()-1))
exu.Print('uTotal=',uTotal)

exu.sys['testResult'] = uTotal
#+++++++++++++++++++++++++++++++++++++++++++++

if not testIsActive:
    if len(sensorNumbers):
        mbs.PlotSensor(sensorNumbers[1],components=[0,1,2])
```