python - 使用 BeautifulSoup 选择特定的 <tr> 标签

Question

我正在使用这段代码用 BeautifulSoup 获取一些 html 表格行:

from bs4 import BeautifulSoup
import urllib2
import re

page = urllib2.urlopen('www.something.bla')
soup = BeautifulSoup(page)
rows = soup.findAll('tr', attrs={'class': re.compile('class1.*')})

这是我得到的结果:

<tr class="class1 class2 class3">...</tr>
<tr class="class1 class2 class3">...</tr>
<tr class="class1 class5">...</tr>
<tr class="class1_a class5_a">...</tr>
<tr class="class1 class5">...</tr>
<tr class="class1_a class5_a">...</tr>
<!-- etc. -->

但是，我想排除(或首先不选择它们)那些具有 class1 class2 class3 作为属性的行。

我该怎么做？
感谢您的帮助!

Answer 1

也许没有正则表达式会更容易。这适用于 BeautifulSoup 3:

from BeautifulSoup import BeautifulSoup

page = """
<tr class="class1 class2 class3">1</tr>
<tr class="class1 class2 class3">2</tr>
<tr class="class1 class5">3</tr>
<tr class="class1_a class5_a">4</tr>
<tr class="class1 class5">5</tr>
<tr class="class1_a class5_a">6</tr>
<tr>7</tr>"""

def cond(x):
    if x:
        return x.startswith("class1") and not "class2 class3" in x
    else:
        return False

soup = BeautifulSoup(page)
rows = soup.findAll('tr', {'class': cond})

for row in rows:
    print row

=>

<tr class="class1 class5">3</tr>
<tr class="class1_a class5_a">4</tr>
<tr class="class1 class5">5</tr>
<tr class="class1_a class5_a">6</tr>

---

使用 BeautifulSoup 4，我能够使其工作如下:

import re
from bs4 import BeautifulSoup

page = """
<tr class="class1 class2 class3">1</tr>
<tr class="class1 class2 class3">2</tr>
<tr class="class1 class5">3</tr>
<tr class="class1_a class5_a">4</tr>
<tr class="class1 class5">5</tr>
<tr class="class1_a class5_a">6</tr>
<tr>7</tr>"""

soup = BeautifulSoup(page)
rows = soup.find_all('tr', {'class': re.compile('class1.*')})

for row in rows:
    cls = row.attrs.get("class")
    if not ("class2" in cls or "class3" in cls):
        print row

=>

<tr class="class1 class5">3</tr>
<tr class="class1_a class5_a">4</tr>
<tr class="class1 class5">5</tr>
<tr class="class1_a class5_a">6</tr>

在 BS4 中，class 等多值属性的值是字符串列表，而不是字符串。参见 http://www.crummy.com/software/BeautifulSoup/bs4/doc/#id12 .