使用Python请求模块的正确的try/except方式是什么？

Question

try:
    r = requests.get(url, params={'s': thing})
except requests.ConnectionError, e:
    print e #should I also sys.exit(1) after this?

这是对的吗？有没有更好的方法来构建这个？这能覆盖我所有的基地吗？

Answer 1

异常对象还包含原始响应e.response，如果需要在服务器的响应中看到错误体，这可能很有用。例如：

try:
    r = requests.post('somerestapi.com/post-here', data={'birthday': '9/9/3999'})
    r.raise_for_status()
except requests.exceptions.HTTPError as e:
    print (e.response.text)

Answer 2

看看请求exception docs。简而言之：

In the event of a network problem (e.g. DNS failure, refused connection, etc), Requests will raise a ConnectionError exception.

In the event of the rare invalid HTTP response, Requests will raise an HTTPError exception.

If a request times out, a Timeout exception is raised.

If a request exceeds the configured number of maximum redirections, a TooManyRedirects exception is raised.

All exceptions that Requests explicitly raises inherit from requests.exceptions.RequestException.

为了回答你的问题，你所展示的将不会覆盖你所有的基础。您将只捕获与连接相关的错误，而不会捕获超时的错误。

捕获异常时的操作实际上取决于脚本/程序的设计。可以离开吗？你能继续再试一次吗？如果错误是灾难性的，并且您不能继续，那么可以调用sys.exit()。

您可以捕获基类异常，它将处理所有情况：

try:
    r = requests.get(url, params={'s': thing})
except requests.exceptions.RequestException as e:  # This is the correct syntax
    print e
    sys.exit(1)

或者你可以单独抓到他们，做不同的事情。

try:
    r = requests.get(url, params={'s': thing})
except requests.exceptions.Timeout:
    # Maybe set up for a retry, or continue in a retry loop
except requests.exceptions.TooManyRedirects:
    # Tell the user their URL was bad and try a different one
except requests.exceptions.RequestException as e:
    # catastrophic error. bail.
    print e
    sys.exit(1)

---

正如Christian所指出的：

If you want http errors (e.g. 401 Unauthorized) to raise exceptions, you can call Response.raise_for_status. That will raise an HTTPError, if the response was an http error.

例如：

try:
    r = requests.get('http://www.google.com/nothere')
    r.raise_for_status()
except requests.exceptions.HTTPError as err:
    print err
    sys.exit(1)

将打印：

404 Client Error: Not Found for url: http://www.google.com/nothere

Answer 3

另一个需要明确的建议。似乎最好是从一堆错误中从一个特定的到另一个通用的，以得到想要捕获的错误，这样特定的错误就不会被通用的错误所掩盖。

url='http://www.google.com/blahblah'

try:
    r = requests.get(url,timeout=3)
    r.raise_for_status()
except requests.exceptions.HTTPError as errh:
    print ("Http Error:",errh)
except requests.exceptions.ConnectionError as errc:
    print ("Error Connecting:",errc)
except requests.exceptions.Timeout as errt:
    print ("Timeout Error:",errt)
except requests.exceptions.RequestException as err:
    print ("OOps: Something Else",err)

Http Error: 404 Client Error: Not Found for url: http://www.google.com/blahblah

对

url='http://www.google.com/blahblah'

try:
    r = requests.get(url,timeout=3)
    r.raise_for_status()
except requests.exceptions.RequestException as err:
    print ("OOps: Something Else",err)
except requests.exceptions.HTTPError as errh:
    print ("Http Error:",errh)
except requests.exceptions.ConnectionError as errc:
    print ("Error Connecting:",errc)
except requests.exceptions.Timeout as errt:
    print ("Timeout Error:",errt)     

OOps: Something Else 404 Client Error: Not Found for url: http://www.google.com/blahblah