选择特定<tr>标签与BeautifulSoup

Question

我的读取与BeautifulSoup一些HTML表行这段代码：

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. --> 

然而，我'想排除（或不首先选择它们）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> 

---

随着BeautifulSoup 4，我能使其工作如下：

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，像class这样的多值属性具有字符串列表作为它们的值，而不是字符串。见http://www.crummy.com/software/BeautifulSoup/bs4/doc/#id12。