mpipython: command not found

Have You tried accessing the binary with the full path?

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 Debian possible default full paths are:

/usr/bin/mpipython - from package: esys-particle

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