pyshell: 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/pyshell - from package: wxPython

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

On Debian possible default full paths are:

/usr/bin/pyshell - from package: python-wxtools

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

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