尝试阻止而不是捕获 - 我是否无意中访问了互联网？

Question

我不小心断开了互联网连接并收到以下错误消息。但是，为什么这个行会触发错误呢？

    self.content += tuple(subreddit_posts)

或者也许我应该问，为什么下面这行 而不是 导致 sys.exit？它似乎应该捕获所有错误：

    try:
        subreddit_posts = self.r.get_content(url, limit=10)
    except:
        print '*** Could not connect to Reddit.'
        sys.exit()

这是否意味着我无意中访问了 reddit 的网络两次？

仅供参考，praw 是一个 reddit API 客户端。 get_content() 获取 subreddit 的 posts/submissons 作为生成器对象。

错误信息：

Traceback (most recent call last):
  File "beam.py", line 49, in <module>
    main()
  File "beam.py", line 44, in main
    scan.scanNSFW()
  File "beam.py", line 37, in scanNSFW
    map(self.getSub, self.nsfw)
  File "beam.py", line 26, in getSub
    self.content += tuple(subreddit_posts)
  File "/Library/Python/2.7/site-packages/praw/__init__.py", line 504, in get_co
    page_data = self.request_json(url, params=params)
  File "/Library/Python/2.7/site-packages/praw/decorators.py", line 163, in wrap
    return_value = function(reddit_session, *args, **kwargs)
  File "/Library/Python/2.7/site-packages/praw/__init__.py", line 557, in reques
    retry_on_error=retry_on_error)
  File "/Library/Python/2.7/site-packages/praw/__init__.py", line 399, in _reque
    _raise_response_exceptions(response)
  File "/Library/Python/2.7/site-packages/praw/internal.py", line 178, in _raise
    response.raise_for_status()
  File "/Library/Python/2.7/site-packages/requests/models.py", line 831, in rais
    raise HTTPError(http_error_msg, response=self)
requests.exceptions.HTTPError: 503 Server Error: Service Unavailable

脚本（很短）：

import sys, os, pprint, praw

class Scanner(object):
    ''' A scanner object. '''
    def __init__(self):
        self.user_agent = 'debian.22990.myapp'
        self.r = praw.Reddit(user_agent=self.user_agent)
        self.nsfw = ('funny', 'nsfw')
        self.nsfw_posters = set()
        self.content = ()

    def getSub(self, subreddit):
        ''' Accepts a subreddit. Connects to subreddit and retrieves content.
        Unpacks generator object containing content into tuple. '''
        url = 'http://www.reddit.com/r/{sub}/'.format(sub=subreddit)
        print 'Scanning:', subreddit
        try:
            subreddit_posts = self.r.get_content(url, limit=10)
        except:
            print '*** Could not connect to Reddit.'
            sys.exit()
        print 'Constructing list.',
        self.content += tuple(subreddit_posts)
        print 'Done.'

    def addNSFWPoster(self, post):
        print 'Parsing author and adding to posters.'
        self.nsfw_posters.add(str(post.author))

    def scanNSFW(self):
        ''' Scans all NSFW subreddits. Makes list of posters.'''
#       Get content from all nsfw subreddits
        print 'Executing map function.'
        map(self.getSub, self.nsfw)
#       Scan content and get authors
        print 'Executing list comprehension.'
        [self.addNSFWPoster(post) for post in self.content]

def main():
    scan = Scanner()
    scan.scanNSFW()
    for i in scan.nsfw_posters:
        print i
    print len(scan.content)

main()

Answer 1

看起来 praw 将延迟获取对象，所以当您实际使用时 subreddit_posts 是在发出请求时，这就解释了为什么它在那条线上爆炸了。

参见：https://praw.readthedocs.org/en/v2.1.20/pages/lazy-loading.html

尝试阻止而不是捕获 - 我是否无意中访问了互联网？

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