vtkpython: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/vtkpython - from package: vtk-python

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/vtkpython - from package: python-vtk

You may install the required package with command apt-get install {package}

Error in other languages:
vtkpython: bevel nie gevind nie
vtkpython: comandă negăsită
vtkpython: comando não encontrado
vtkpython: commande introuvable
vtkpython: command not found
vtkpython: käsku ei ole
vtkpython: không tìm thấy lệnh
vtkpython: komanda nerasta
vtkpython: Kommando nicht gefunden.
vtkpython: kommandot finns inte
vtkpython: komut yok
vtkpython: nie znaleziono polecenia
vtkpython: níor aimsíodh an t-ordú
vtkpython: no se encontró la orden
vtkpython: no s'ha trobat l'ordre
vtkpython: opdracht niet gevonden
vtkpython: parancs nem található
vtkpython: perintah tidak ditemukan
vtkpython: príkaz nenájdený
vtkpython: příkaz nenalezen
vtkpython: команда не найдена
vtkpython: командата не е открита
vtkpython: 命令找不到
vtkpython: コマンドが見つかりません