Ubuntu 13.10: edit shell prompt path

small tips.

how to edit prompt shell ( PS1,PS2 ..etc)

root@note:/home/hattori/Python_works# cat /etc/environment
PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games"
PS1='\u@\h:\W: '
export PS1
root@note:/home/hattori/Python_works#

root@note:/home/hattori/Python_works# source /etc/environment
root@note:Python_works:

root@note:Python_works: echo $PS1

\u@\h:\W:

user@host: Currenty working directory: