实现功能：

利用 paramiko 模块实现

1.远程目录检索

2.远程文件下载

3.远程目录下载（带目录结构）

class SFTPConnection(object):    def __init__(self, host, username, password, port=22):        try:            self.transport = paramiko.Transport(sock=(host, port))            self.transport.connect(username=username, password=password)            self.sftp = paramiko.SFTPClient.from_transport(self.transport)        except Exception, e:            traceback.print_exc()            sys.stderr.write("%s\n" % e)            sys.exit(-1)    def __del__(self):        if self.transport:            self.transport.close()    def traverse_directory(self, base_dir, deep=1):        """Traverse directory"""        dir_stru = {}        base_dir_name = os.path.basename(base_dir)        dir_list = self.sftp.listdir(base_dir)        for dir_name in dir_list:            dir_path = os.path.join(base_dir, dir_name)            if not self._is_file(dir_path):                if deep > 1:                    dir_stru.setdefault(base_dir_name, []).append(self.traverse_directory(base_dir=dir_path,                                                                                          deep=deep - 1))                else:                    dir_stru.setdefault(base_dir_name, []).append(dir_name)            else:                dir_stru.setdefault(base_dir_name, []).append(dir_name)        if not dir_list:            dir_stru.setdefault(base_dir_name, []).append("")        return dir_stru    def _is_file(self, file_path):        if not self._exist_path(file_path):            sys.stderr.write("File path is not exist.[%s]\n" % file_path)            return None        return not stat.S_ISDIR(self.sftp.stat(file_path).st_mode)    def _exist_path(self, file_path):        try:            file_stat = self.sftp.stat(file_path)            return True        except IOError, e:            traceback.print_exc()            sys.stderr.write("%s\n" % e)            return False    def file_downloader(self, file_path_src, file_dir_des):        file_path_des = os.path.join(file_dir_des, os.path.basename(file_path_src))        if os.path.exists(file_path_des):            sys.stderr.write("Download File[%s] have exist. Pass it.\n" % file_path_des)            return        if not self._exist_path(file_path_src) or not self._is_file(file_path_src):            sys.stderr.write("File[%s] is not exist or is not a file.\n" % file_path_src)            sys.exit(-1)        if not os.path.exists(file_dir_des):            os.mkdir(file_dir_des)        sys.stdout.write("File[%s] size is %s \n" % (file_path_src, pretty_size(self.sftp.stat(file_path_src).st_size)))        self.sftp.get(file_path_src, file_path_des)        sys.stdout.write("Download file[%s] to [%s] done.\n" % (file_path_src, file_path_des))    def directory_download(self, dir_path_src, dir_path_des):        if not self._exist_path(dir_path_src):            sys.stderr.write("path[%s] is not exist in remote machine.\n" % dir_path_src)            sys.exit(-1)        if not os.path.exists(dir_path_des):            os.mkdir(dir_path_des)        for sub_dir_name in self.sftp.listdir(dir_path_src):            sub_dir_path = os.path.join(dir_path_src, sub_dir_name)            if self._is_file(sub_dir_path):                self.file_downloader(sub_dir_path, dir_path_des)            else:                self.directory_download(sub_dir_path, os.path.join(dir_path_des, sub_dir_name))        sys.stdout.write("Download data from directory[%s] to [%s] done.\n" % (dir_path_src, dir_path_des))