#!/usr/bin/python

-- coding: utf-8 --
import ftplib
import os
import socket
HOST = 'ftp.mozilla.org'
DIRN = 'pub/mozilla.org/webtools'
FILE = 'bugzilla-3.6.9-to-3.6.10-nodocs.diff.gz'
def writedata(data):
    f = open(FILE,'wb')
    try:
        f.write(data)
    finally:
        f.close()
def main():
    try:
        f = ftplib.FTP(HOST)
    except (socket.error, socket.gaierror):
        print 'ERROR:cannot reach " %s"' % HOST
        return
    print '***Connected to host "%s"' % HOST

try:
    f.login()
except ftplib.error_perm:
    print 'ERROR: cannot login anonymously'
    f.quit()
    return
print '*** Logged in as "anonymously"'

try:
    f.cwd(DIRN)
except ftplib.error_perm:
    print 'ERRORL cannot CD to "%s"' % DIRN
    f.quit()
    return
print '*** Changed to "%s" folder' % DIRN

try:
    #傳一個回調函數給retrbinary() 它在每接收一個二進制數據時都會被調用
    f.retrbinary('RETR %s' %FILE, writedata)
except ftplib.error_perm:
    print 'ERROR: cannot read file "%s"' %FILE
    os.unlink(FILE)
else:
    print '*** Downloaded "%s" to CWD' % FILE

f.quit()
return


if name == 'main':
    main()</pre>