idle3: 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 Debian possible default full paths are:

/usr/bin/idle3 - from package: idle3

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

Error in other languages:
idle3: bevel nie gevind nie
idle3: comandă negăsită
idle3: comando não encontrado
idle3: commande introuvable
idle3: command not found
idle3: käsku ei ole
idle3: không tìm thấy lệnh
idle3: komanda nerasta
idle3: Kommando nicht gefunden.
idle3: kommandot finns inte
idle3: komut yok
idle3: nie znaleziono polecenia
idle3: níor aimsíodh an t-ordú
idle3: no se encontró la orden
idle3: no s'ha trobat l'ordre
idle3: opdracht niet gevonden
idle3: parancs nem található
idle3: perintah tidak ditemukan
idle3: príkaz nenájdený
idle3: příkaz nenalezen
idle3: команда не найдена
idle3: командата не е открита
idle3: 命令找不到
idle3: コマンドが見つかりません