mpdhelp.py: 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/mpdhelp.py - from package: mpich2

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

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