我正在嘗試在代碼中插入一個(gè)變量以在遠(yuǎn)程 Linux 主機(jī)上運(yùn)行命令，為此我使用 .format 方法，請(qǐng)參閱下面的代碼：import paramikofrom datetime import datetime, timedeltahostnames = [   'hostname',]username = 'username'password = 'password'ssh = paramiko.SSHClient()ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())ssh.load_system_host_keys()ydate = datetime.strftime(datetime.now() - timedelta(1), '%Y%m%d')for host in hostnames:   ssh.connect(host, username=username, password=password, look_for_keys=False)   ssh.exec_command('cp test.txt {}.mrs_stats0.{}.pytest.gz ; chmod +r {}.mrs_stats0.{}s.gz').format(host, ydate, host, ydate)我在嘗試使用 {} 和 .format 時(shí)失敗，并出現(xiàn)以下錯(cuò)誤：Traceback (most recent call last):  File "C:/Users/IdeaProjects/main.py", line 25, in <module>    ssh.exec_command('cp test.txt {}.mrs_stats0.{}.pytest.gz ; chmod +r {}.mrs_stats0.{}s.gz').format(host, test, host, test)AttributeError: 'tuple' object has no attribute 'format'我無(wú)法理解為什么我收到此錯(cuò)誤，此外我已經(jīng)做了一些閱讀以進(jìn)一步理解元組，并且我無(wú)法理解為什么我的變量沒(méi)有被讀取為字符串