Python urllib.urlopen IOError错误

Question

我在一个函数里写了以下几行代码：

sock = urllib.urlopen(url)
html = sock.read()
sock.close()

当我手动调用这个函数时，它运行得很好。但是，当我在一个循环里调用这个函数（用的还是之前的那些网址）时，我遇到了以下错误：

> Traceback (most recent call last):
  File "./headlines.py", line 256, in <module>
    main(argv[1:])
  File "./headlines.py", line 37, in main
    write_articles(headline, output_folder + "articles_" + term +"/")
  File "./headlines.py", line 232, in write_articles
    print get_blogs(headline, 5)
  File "/Users/michaelnussbaum08/Documents/College/Sophmore_Year/Quarter_2/Innovation/Headlines/_code/get_content.py", line 41, in get_blogs
    sock = urllib.urlopen(url)
  File "/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/urllib.py", line 87, in urlopen
    return opener.open(url)
  File "/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/urllib.py", line 203, in open
    return getattr(self, name)(url)
  File "/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/urllib.py", line 314, in open_http
    if not host: raise IOError, ('http error', 'no host given')
IOError: [Errno http error] no host given

有没有什么想法？

补充更多代码：

def get_blogs(term, num_results):
    search_term = term.replace(" ", "+")
    print "search_term: " + search_term
    url = 'http://blogsearch.google.com/blogsearch_feeds?hl=en&q='+search_term+'&ie=utf-8&num=10&output=rss'
    print "url: " +url  

    #error occurs on line below

    sock = urllib.urlopen(url)
    html = sock.read()
    sock.close()

def write_articles(headline, output_folder, num_articles=5):

    #calls get_blogs

    if not os.path.exists(output_folder):
    os.makedirs(output_folder)

    output_file = output_folder+headline.strip("\n")+".txt"
    f = open(output_file, 'a')
    articles = get_articles(headline, num_articles)
    blogs = get_blogs(headline, num_articles)


    #NEW FUNCTION
    #the loop that calls write_articles
    for term in trend_list: 
        if do_find_max == True:
        fill_search_term(term, output_folder)
    headlines = headline_process(term, output_folder, max_headlines, do_find_max)
    for headline in headlines:
    try:
        write_articles(headline, output_folder + "articles_" + term +"/")
    except UnicodeEncodeError:
        pass

Answer 1

在你函数的循环里，调用 urlopen 之前，可以加一句打印语句：

print(url)
sock = urllib.urlopen(url)

这样，当你运行这个脚本并遇到 IOError 错误时，你就能看到导致问题的 url。如果 url 是类似 'http://' 这样的内容，就会出现 "没有提供主机" 的错误。

Answer 2

我遇到了一个问题，就是我在把一个变量和网址拼接在一起时，那个变量，比如说 search_term

url = 'http://blogsearch.google.com/blogsearch_feeds?hl=en&q='+search_term+'&ie=utf-8&num=10&output=rss'

最后多了一个换行符。所以你要确保你做了

search_term = search_term.strip()

你可能还想做一下

search_term = urllib2.quote(search_term)

这样可以确保你的字符串在网址中是安全的

Answer 3

如果你不想自己处理逐块读取数据，可以使用urllib2。这样做可能会更符合你的预期。

import urllib2
req = urllib2.Request(url='http://stackoverflow.com/')
f = urllib2.urlopen(req)
print f.read()