# How can I create a time dependent vtkUnstructuredGrid object?
**URL:** https://discourse.vtk.org/t/how-can-i-create-a-time-dependent-vtkunstructuredgrid-object/1822
**Category:** Support
**Created:** [September 25, 2019, 7:40pm UTC](https://discourse.vtk.org/t/how-can-i-create-a-time-dependent-vtkunstructuredgrid-object/1822 "2019-09-25T19:40:13Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@myousefi2016](https://discourse.vtk.org/u/myousefi2016)
#### Post date: [September 25, 2019, 7:40pm UTC](https://discourse.vtk.org/t/how-can-i-create-a-time-dependent-vtkunstructuredgrid-object/1822/1 "2019-09-25T19:40:13Z")
Currently, I’m combining some vtu files that belong to different time snapshots into one vtu file by using this function:
```auto
def Combiner(mainfiles,path):
data_to_write = vtk.vtkUnstructuredGrid()
writer = vtk.vtkXMLUnstructuredGridWriter()
writer.SetNumberOfTimeSteps(len(mainfiles))
writer.SetInputData(data_to_write)
writer.SetFileName(path)
writer.Start()
for i,filev in enumerate(mainfiles):
print "Writing Timestep: " + str(i)
data_to_write.ShallowCopy(vtkReader(filev))
writer.WriteNextTime(i)
writer.Stop()
ug = vtkReader(path)
os.remove(path)
return ug
```
As you can see I need to write the combined vtu file and load it again, which is pretty slow. Is there any way to get away with writing stuff into the disk?
---
### Author:  [@Aron\_Helser](https://discourse.vtk.org/u/Aron_Helser)
#### Post date: [September 26, 2019, 5:06pm UTC](https://discourse.vtk.org/t/how-can-i-create-a-time-dependent-vtkunstructuredgrid-object/1822/2 "2019-09-26T17:06:34Z")
You could certainly do this with a multi-block file, which you could just update to point to each of the sub-files. But I don’t know how to specify the time steps in that case. I do think that’s possible, though.
In ParaView, sequentially numbered files will be automatically read in as a time-series…
-Aron