Python FTP download

I just learned chapter 1 of "Python core programming", FTP programming, and wrote a small script to download all the files on the FTP website. I haven't learned multi-thread programming yet, multi‑thread download will be added later.

from ftplib import FTPimport reimport oshost = 'ftp.neu.edu.cn'dir_path = '/ebook/python'def get_filename(string):    patt = re.compile(r'2011\s(.+)')    filename = re.findall(patt, string)[0]    return filename    def main():    filenames = []    try:        fp = FTP(host)    except Exception:        print "can not connect to ",host        return     print 'connect to ',host,' successfully'    try:        fp.login()    except Exception:        print 'login failed'        return     print 'login successfully'        try:        fp.cwd(dir_path)    except Exception:        print 'change to directory:',dir_path," failed"        fp.quit()        return    print 'change to directory %s successfully' %(fp.pwd())        fp.retrlines('LIST',lambda x:filenames.append(get_filename(x)))    """for filename in filenames:        print filename    return     """    for filename in filenames:        try:            fp.retrbinary('RETR %s' %filename, open(filename,'wb').write)        except Exception ,e:            print e        print '%s download successfully' % filename    fp.quit()    print 'all file download successfully'if __name__ == "__main__":    main()