parallel_alpha_diversity.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 Debian possible default full paths are:

/usr/lib/qiime/bin/parallel_alpha_diversity.py - from package: qiime

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

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