Beautifulsoup在while循环中调用时返回相同的结果

Question

我是python的新手,并尝试编写一个剪贴板来获取页面上的所有链接多个分页.我在while循环中调用以下代码.

page = urllib2.urlopen(givenurl,"",10000)

soup = BeautifulSoup(page, "lxml")

linktags = soup.findAll('span',attrs={'class':'paginationLink pageNum'}) 

page.close()

BeautifulSoup.clear(soup)

return linktags

它总是返回我传递的第一个url的结果.难道我做错了什么？

Answer 1

@uncollected可能在评论中找到了正确的答案,但我想扩展它.

如果您正在调用确切的代码,但嵌套在一个while块中,它将立即返回第一个结果.你可以在这做两件事.

我不确定你是如何while在你自己的上下文中使用的,所以我在for这里使用循环.

扩展结果列表,并返回整个列表

def getLinks(urls):
    """ processes all urls, and then returns all links """
    links = []
    for givenurl in urls:
        page = urllib2.urlopen(givenurl,"",10000)
        soup = BeautifulSoup(page, "lxml")
        linktags = soup.findAll('span',attrs={'class':'paginationLink pageNum'}) 
        page.close()
        BeautifulSoup.clear(soup)
        links.extend(linktags)
        # dont return here or the loop is over

    return links

或者,不是返回,而是使用yield关键字使其成为生成器.生成器将返回每个结果并暂停直到下一个循环:

def getLinks(urls):
    """ generator yields links from one url at a time """
    for givenurl in urls:
        page = urllib2.urlopen(givenurl,"",10000)
        soup = BeautifulSoup(page, "lxml")
        linktags = soup.findAll('span',attrs={'class':'paginationLink pageNum'}) 
        page.close()
        BeautifulSoup.clear(soup)
        # this will return the current results,
        # and pause the state, until the the next
        # iteration is requested    
        yield linktags