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python - 处理来自 python 请求的异常

问题描述

我的函数是用线程执行的：

def getdata(self, page, ...):
    tries = 10
    for n in range(tries):
        try:
            ...
            datarALL = []
            url = 'http://website/...'.format(...)
            responsedata = requests.get(url, data=data, headers=self.hed, verify=False)
            responsedata.raise_for_status()
            if responsedata.status_code == 200:  # 200 for successful call
                ...
                    if ...
                        break   
        except (ChunkedEncodingError, requests.exceptions.HTTPError) as e:
            print ("page #{0} run #{1} failed. Returned status code {2}. Reason: {3}. Msg: {4}. Retry.".format(page, n, responsedata.status_code, responsedata.reason, sys.exc_info()[0]))
            if n == tries - 1:
                print ("page {0} could not be imported. Max retried reached.".format(page))
                os._exit(1)  #One thread max retried - close all threads and 
    return datarALL

如下：

    with ThreadPoolExecutor(max_workers=num_of_workers) as executor:
        futh = [(executor.submit(self.getdata, page,...)) for page in pages]
        for data in as_completed(futh):
            datarALL.extend(data.result())
    print ("Finished generateing data.")
    return datarALL

有时我会遇到意想不到的异常ConnectionResetError: [Errno 104] Connection reset by peer，例如：关闭我的程序。我想更改我的代码，以便无论发生哪种异常，线程都会重试直到if n == tries - 1:满足。我不希望我的线程由于随机异常而关闭。

我阅读了请求异常信息页面，但我不知道如何在不手动列出所有异常的情况下捕获所有异常。有没有通用的方法来做到这一点？

基本上我想要类似的东西：

        except (ALL EXCEPTIONS from Requests) as e:
            print ("page #{0} run #{1} failed. Returned status code {2}. Reason: {3}. Msg: {4}. Retry.".format(page, n, responsedata.status_code, responsedata.reason, sys.exc_info()[0]))
            if n == tries - 1:
                print ("page {0} could not be imported. Max retried reached.".format(page))
                os._exit(1)  #One thread max retried - close all threads and 
    return datarALL

我怎样才能做到这一点？

编辑： 使用

    except Exception as e:
        print ("page #{0} run #{1} failed. Returned status code {2}. Reason: {3}. Msg: {4}. Retry.".format(page, n, responsedata.status_code, responsedata.reason, sys.exc_info()[0]))
        if n == tries - 1:
            print ("page {0} could not be imported. Max retried reached.".format(page))
            os._exit(1)  #One thread max retried - close all threads and 
return datarALL

不抓。它给了我这个：

Traceback (most recent call last):
  File "/home/ubuntu/.local/lib/python3.5/site-packages/urllib3/response.py", line 331, in _error_catcher
    yield
  File "/home/ubuntu/.local/lib/python3.5/site-packages/urllib3/response.py", line 640, in read_chunked
    chunk = self._handle_chunk(amt)
  File "/home/ubuntu/.local/lib/python3.5/site-packages/urllib3/response.py", line 595, in _handle_chunk
    returned_chunk = self._fp._safe_read(self.chunk_left)
  File "/usr/lib/python3.5/http/client.py", line 607, in _safe_read
    chunk = self.fp.read(min(amt, MAXAMOUNT))
  File "/usr/lib/python3.5/socket.py", line 575, in readinto
    return self._sock.recv_into(b)
ConnectionResetError: [Errno 104] Connection reset by peer

循环不会重试。运行终止...

编辑2：

    except requests.exceptions.RequestException as e:
        print ("page #{0} run #{1} failed. Returned status code {2}. Reason: {3}. Msg: {4}. Retry.".format(page, n, responsedata.status_code, responsedata.reason, sys.exc_info()[0]))
        if n == tries - 1:
            print ("page {0} could not be imported. Max retried reached.".format(page))
            os._exit(1)  #One thread max retried - close all threads and 
return datarALL

也没有赶上ConnectionResetError: [Errno 104] Connection reset by peer上面列出的。

标签： pythonpython-requests

解决方案

捕获所有异常通常被认为是一种不好的做法，因为它可能会隐藏一些问题。

也就是说，Python 异常受益于继承，并且捕获基本异常将捕获从该基本异常继承的每个异常。

有关详细信息，请参阅Python 标准异常层次结构。

您可以看到根异常是BaseException，但永远不应该捕获这个异常，因为它会捕获Ctrl+C中断和生成器退出。如果你想捕捉每一个异常类型，你可以捕捉Exception.

您也可能只想从requests. 在这种情况下，根据doc，可以通过捕获requests模块的基本异常来完成：RequestException

如果你想同时捕获requests异常和ConnectionResetError（这是一个 Python 标准异常），你必须在你的except子句中同时指定：

except (requests.exceptions.RequestException,
        ConnectionResetError) as err:
    # some code

或者，如果您想不那么具体并捕获所有可能的连接错误，您可以使用ConnectionError而不是ConnectionResetError. （请参阅异常层次结构）

最后，您可能希望对每种异常类型做出不同的反应。在这种情况下，您可以这样做：

try:
    # something
except ConnectionError as err:
    # manage connection errors
except requests.exceptions.RequestException as err:
    # manage requests errors

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