即使使用 try/except 语句捕获 Python 中的异常，程序也有可能崩溃吗？

Is it possible for program to crash even with try/except statement that captures Exception in Python?

提问人：Jack McGowan 提问时间：6/29/2023 最后编辑：Jack McGowan 更新时间：6/29/2023 访问量：67

问：

我正在创建一些自动化，可以在某个时间点重新启动设备。为了在重新启动后重新连接，我想在等待一段时间后继续尝试连接，直到它最终重新连接。由于重新连接失败时会出现错误，因此我认为我可以捕获所有异常，然后只是休眠一段时间，然后再次运行连接代码并继续此循环。但是，我的程序在到达连接错误后仍然崩溃。是否只是有一些例外情况无法捕捉到？

这是我为参考而创建的函数，但我仍然只是收到一堆不同的错误，例如 、 、 和requests.exceptions.ConnectionErrorurllib3.exceptions.MaxRetryErrorurllib3.exceptions.NewConnectionErrorConnectionRefusedError

def establish_session(device):
    try:
        sess = IdentityServicesEngineAPI(username=config.username,
                                    password=config.password,
                                    base_url='https://' + device,
                                    verify=False)
    except Exception as e:
        print("connection refused. node rebooting. Trying again in 60 seconds")
        time.sleep(60)
        return establish_session(device) # Nested here...

    return sess

任何反馈将不胜感激

更新：添加完整回溯。

Traceback (most recent call last):
  File "/python3.10/site-packages/urllib3/connection.py", line 174, in _new_conn
    conn = connection.create_connection(
  File "/python3.10/site-packages/urllib3/util/connection.py", line 95, in create_connection
    raise err
  File "/python3.10/site-packages/urllib3/util/connection.py", line 85, in create_connection
    sock.connect(sa)
ConnectionRefusedError: [Errno 61] Connection refused

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/python3.10/site-packages/urllib3/connectionpool.py", line 714, in urlopen
    httplib_response = self._make_request(
  File "/python3.10/site-packages/urllib3/connectionpool.py", line 403, in _make_request
    self._validate_conn(conn)
  File "/python3.10/site-packages/urllib3/connectionpool.py", line 1053, in _validate_conn
    conn.connect()
  File "/python3.10/site-packages/urllib3/connection.py", line 363, in connect
    self.sock = conn = self._new_conn()
  File "/python3.10/site-packages/urllib3/connection.py", line 186, in _new_conn
    raise NewConnectionError(
urllib3.exceptions.NewConnectionError: <urllib3.connection.HTTPSConnection object at 0x104e2b670>: Failed to establish a new connection: [Errno 61] Connection refused

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/python3.10/site-packages/requests/adapters.py", line 486, in send
    resp = conn.urlopen(
  File "/python3.10/site-packages/urllib3/connectionpool.py", line 798, in urlopen
    retries = retries.increment(
  File "/python3.10/site-packages/urllib3/util/retry.py", line 592, in increment
    raise MaxRetryError(_pool, url, error or ResponseError(cause))
urllib3.exceptions.MaxRetryError: HTTPSConnectionPool(host='device1', port=443): Max retries exceeded with url: /api/v1/task (Caused by NewConnectionError('<urllib3.connection.HTTPSConnection object at 0x104e2b670>: Failed to establish a new connection: [Errno 61] Connection refused'))

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/python3.10/site-packages/ciscoisesdk/restsession.py", line 497, in request
    response = self._req_session.request(method, abs_url, **kwargs)
  File "/python3.10/site-packages/requests/sessions.py", line 589, in request
    resp = self.send(prep, **send_kwargs)
  File "/python3.10/site-packages/requests/sessions.py", line 703, in send
    r = adapter.send(request, **kwargs)
  File "/python3.10/site-packages/requests/adapters.py", line 519, in send
    raise ConnectionError(e, request=request)
requests.exceptions.ConnectionError: HTTPSConnectionPool(host='device1', port=443): Max retries exceeded with url: /api/v1/task (Caused by NewConnectionError('<urllib3.connection.HTTPSConnection object at 0x104e2b670>: Failed to establish a new connection: [Errno 61] Connection refused'))

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/python3.10/site-packages/urllib3/connection.py", line 174, in _new_conn
    conn = connection.create_connection(
  File "/python3.10/site-packages/urllib3/util/connection.py", line 95, in create_connection
    raise err
  File "/python3.10/site-packages/urllib3/util/connection.py", line 85, in create_connection
    sock.connect(sa)
ConnectionRefusedError: [Errno 61] Connection refused

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/python3.10/site-packages/urllib3/connectionpool.py", line 714, in urlopen
    httplib_response = self._make_request(
  File "/python3.10/site-packages/urllib3/connectionpool.py", line 403, in _make_request
    self._validate_conn(conn)
  File "/python3.10/site-packages/urllib3/connectionpool.py", line 1053, in _validate_conn
    conn.connect()
  File "/python3.10/site-packages/urllib3/connection.py", line 363, in connect
    self.sock = conn = self._new_conn()
  File "/python3.10/site-packages/urllib3/connection.py", line 186, in _new_conn
    raise NewConnectionError(
urllib3.exceptions.NewConnectionError: <urllib3.connection.HTTPSConnection object at 0x104e29930>: Failed to establish a new connection: [Errno 61] Connection refused

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/lib/python3.10/site-packages/requests/adapters.py", line 486, in send
    resp = conn.urlopen(
  File "/python3.10/site-packages/urllib3/connectionpool.py", line 798, in urlopen
    retries = retries.increment(
  File "/python3.10/site-packages/urllib3/util/retry.py", line 592, in increment
    raise MaxRetryError(_pool, url, error or ResponseError(cause))
urllib3.exceptions.MaxRetryError: HTTPSConnectionPool(host='device1', port=443): Max retries exceeded with url: /api/v1/task (Caused by NewConnectionError('<urllib3.connection.HTTPSConnection object at 0x104e29930>: Failed to establish a new connection: [Errno 61] Connection refused'))

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/lib/python3.10/site-packages/ciscoisesdk/restsession.py", line 504, in request
    response = self._req_session.request(method, abs_url,
  File "/python3.10/site-packages/requests/sessions.py", line 589, in request
    resp = self.send(prep, **send_kwargs)
  File "/python3.10/site-packages/requests/sessions.py", line 703, in send
    r = adapter.send(request, **kwargs)
  File "/python3.10/site-packages/requests/adapters.py", line 519, in send
    raise ConnectionError(e, request=request)
requests.exceptions.ConnectionError: HTTPSConnectionPool(host='device1', port=443): Max retries exceeded with url: /api/v1/task (Caused by NewConnectionError('<urllib3.connection.HTTPSConnection object at 0x104e29930>: Failed to establish a new connection: [Errno 61] Connection refused'))

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/Pre_Post_Checks_Automation/test_api_calls.py", line 5, in <module>
    hold = api.tasks.get_task_status().response
  File "python3.10/site-packages/ciscoisesdk/api/v3_1_patch_1/tasks.py", line 123, in get_task_status
    _api_response = self._session.get(endpoint_full_url, params=_params)
  File "/python3.10/site-packages/ciscoisesdk/restsession.py", line 609, in get
    response = self.request('GET', url, erc, 0, params=params, **kwargs)
  File "python3.10/site-packages/ciscoisesdk/restsession.py", line 507, in request
    raise ciscoisesdkException('Socket error {}'.format(e))
ciscoisesdk.exceptions.ciscoisesdkException: Socket error HTTPSConnectionPool(host='device1', port=443): Max retries exceeded with url: /api/v1/task (Caused by NewConnectionError('<urllib3.connection.HTTPSConnection object at 0x104e29930>: Failed to establish a new connection: [Errno 61] Connection refused'))
python-3.x 异常

评论

1赞 quamrana 6/29/2023
另一方面，您是递归调用，这是无缘无故地使用堆栈。然后，如果重试成功，并且 u ，则该变量将丢失。你的意思是写：establish_session(device)return sessreturn establish_session(device) # Nested here...
0赞 Joran Beasley 6/29/2023
你能发布你的实际回溯吗？
0赞 Jack McGowan 6/29/2023
@quamrana 啊，是的，我明白了。谢谢。老实说，这可能会解决所有问题，因为程序的其余部分将能够使用该连接。将很快更新帖子
2赞 juanpethes 6/29/2023
在完全不同的音符上，要回答标题中的问题，是的，有些例外不是.例如，和 不是 的子类，而是 的子类，这意味着它们不会被子句捕获。ExceptionGeneratorExitKeyboardInterruptSystemExitExceptionBaseExceptionexcept Exception
1赞 Jack McGowan 6/29/2023
@juanpethes 回答了我的问题。不确定如何关闭此问题并标记为已读，因为它在评论中。对不起，这一切是新的。

答：

1赞 juanpethes 6/29/2023 #1

要回答标题中的问题，是的，有些例外不是.例如，和 不是 的子类，而是 的子类，这意味着它们不会被子句捕获。ExceptionGeneratorExitKeyboardInterruptSystemExitExceptionBaseExceptionexcept Exception

有关内置异常的层次结构，请参阅此内容：

https://docs.python.org/3/library/exceptions.html#exception-hierarchy

以及来自 mCoding 的这个非常有用的视频：

https://www.youtube.com/watch?v=zrVfY9SuO64

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