Python 使用 lxml 遍历部分

Question

我有一个网页，我目前正在使用 BeautifulSoup 解析它，但它很慢，所以我决定尝试 lxml，因为我阅读它非常快。

无论如何，我正在努力让我的代码遍历我想要的部分，不知道如何使用 lxml，而且我找不到明确的文档。

无论如何，这是我的代码：

import urllib, urllib2
from lxml import etree

def wgetUrl(target):
    try:
        req = urllib2.Request(target)
        req.add_header('User-Agent', 'Mozilla/5.0 (Windows; U; Windows NT 5.1; en-GB; rv:1.9.0.3 Gecko/2008092417 Firefox/3.0.3')
        response = urllib2.urlopen(req)
        outtxt = response.read()
        response.close()
    except:
        return ''
    return outtxt

newUrl = 'http://www.tv3.ie/3player'

data = wgetUrl(newUrl)
parser = etree.HTMLParser()
tree   = etree.fromstring(data, parser)

for elem in tree.iter("div"):
    print elem.tag, elem.attrib, elem.text

这会返回所有 DIV，但我如何指定只遍历 dev id='slider1'？

div {'style': 'position: relative;', 'id': 'slider1'} None

这不起作用：

for elem in tree.iter("slider1"):

我知道这可能是一个愚蠢的问题，但我想不通..

谢谢！

* 编辑 **

在您添加此代码的帮助下，我现在得到以下输出：

for elem in tree.xpath("//div[@id='slider1']//div[@id='gridshow']"):
    print elem[0].tag, elem[0].attrib, elem[0].text
    print elem[1].tag, elem[1].attrib, elem[1].text
    print elem[2].tag, elem[2].attrib, elem[2].text
    print elem[3].tag, elem[3].attrib, elem[3].text
    print elem[4].tag, elem[4].attrib, elem[4].text

输出：

a {'href': '/3player/show/392/57922/1/Tallafornia', 'title': '3player | Tallafornia, 11/01/2013. The Tallafornia crew are back, living in a beachside villa in Santa Ponsa, Majorca. As the crew settle in, the egos grow bigger than ever and cause tension'} None
h3 {} None
span {'id': 'gridcaption'} The Tallafornia crew are back, living in a beachside vill...
span {'id': 'griddate'} 11/01/2013
span {'id': 'gridduration'} 00:27:52

这太棒了，但我错过了上面的 a 标签的一部分。解析器会不会正确处理代码？

我没有收到以下信息：

<img alt="3player | Tallafornia, 11/01/2013. The Tallafornia crew are back, living in a beachside villa in Santa Ponsa, Majorca. As the crew settle in, the egos grow bigger than ever and cause tension" src='http://content.tv3.ie/content/videos/0378/tallaforniaep2_fri11jan2013_3player_1_57922_180x102.jpg' class='shadow smallroundcorner'></img>

任何想法为什么它不拉这个？

再次感谢，非常有用的帖子..

Answer 1

您可以按如下方式使用 XPath 表达式：

for elem in tree.xpath("//div[@id='slider1']"):

例子：

>>> import urllib2
>>> import lxml.etree
>>> url = 'http://www.tv3.ie/3player'
>>> data = urllib2.urlopen(url)
>>> parser = lxml.etree.HTMLParser()
>>> tree = lxml.etree.parse(data,parser)
>>> elem = tree.xpath("//div[@id='slider1']")
>>> elem[0].attrib
{'style': 'position: relative;', 'id': 'slider1'}

---

您需要更好地分析您正在处理的页面的内容（一个很好的方法是使用带有 Firebug 插件的 Firefox）。

您尝试获取的<img> 标签实际上是<a> 标签的子标签：

>>> for elem in tree.xpath("//div[@id='slider1']//div[@id='gridshow']"):
...    for elem_a in elem.xpath("./a"):
...       for elem_img in elem_a.xpath("./img"):
...          print '<A> HREF=%s'%(elem_a.attrib['href'])
...          print '<IMG> ALT="%s"'%(elem_img.attrib['alt'])
<A> HREF=/3player/show/392/58784/1/Tallafornia
<IMG> ALT="3player | Tallafornia, 01/02/2013. A fresh romance blossoms in the Tallafornia house. Marc challenges Cormac to a 'bench off' in the gym"
<A> HREF=/3player/show/46/58765/1/Coronation-Street
<IMG> ALT="3player | Coronation Street, 01/02/2013. Tyrone bumps into Kirsty in the street and tries to take Ruby from her pram"
../..

Answer 2

这就是我为自己工作的方式，我不确定这是否是最好的方法，所以欢迎 cmets：

import urllib2, re
from lxml import etree
from datetime import datetime

def wgetUrl(target):
    try:
        req = urllib2.Request(target)
        req.add_header('User-Agent', 'Mozilla/5.0 (Windows; U; Windows NT 5.1; en-GB; rv:1.9.0.3 Gecko/2008092417 Firefox/3.0.3')
        response = urllib2.urlopen(req)
        outtxt = response.read()
        response.close()
    except:
        return ''
    return outtxt

start = datetime.now()

newUrl = 'http://www.tv3.ie/3player' # homepage

data = wgetUrl(newUrl)
parser = etree.HTMLParser()
tree   = etree.fromstring(data, parser)

for elem in tree.xpath("//div[@id='slider1']//div[@id='gridshow'] | //div[@id='slider1']//div[@id='gridshow']//img[@class='shadow smallroundcorner']"):
    if elem.tag == 'img':
        img = elem.attrib.get('src')
        print 'img: ', img

    if elem.tag == 'div':
        show = elem[0].attrib.get('href')
        print 'show: ', show
        titleData = elem[0].attrib.get('title')

        match=re.search("3player\s+\|\s+(.+),\s+(\d\d/\d\d/\d\d\d\d)\.\s*(.*)", titleData) 
        title=match.group(1)
        print 'title: ', title

        description = match.group(3)
        print 'description: ', description

        date = elem[3].text
        duration = elem[4].text
        print 'date: ', date
        print 'duration: ', duration

end = datetime.now()
print 'time took was ', (end-start)

时间安排非常好，尽管与 BeautifulSoup 相比并没有我预期的大差异..