smoothing a dem with a 3x3 kernel window

Hello to everyone ,

sorry if i may sound so basic but the truth is that i just started python scripting . my question is that , i have a dem and 3x3 kernel window. i want to use the weight to smooth the dem. I have seen a tutorial using gdal. but i believe with numpy and arcpy , i should
be able to smooth the dem without the gdal approach.
I would be grateful if you can assist me.:o
thanks