One line ftp server in python

Obligatory Twisted example:

twistd -n ftp

And probably useful:

twistd ftp --help

Usage: twistd [options] ftp [options].
WARNING: This FTP server is probably INSECURE do not use it.
Options:
  -p, --port=           set the port number [default: 2121]
  -r, --root=           define the root of the ftp-site. [default:
                    /usr/local/ftp]
  --userAnonymous=  Name of the anonymous user. [default: anonymous]
  --password-file=  username:password-style credentials database
  --version         
  --help            Display this help and exit.