Web Scraping with Python第二章

1.BeautifulSoup对象类型

• BeautifulSoup对象，例如bsObj.div.h1
• tag对象，例如使用find或findAll函数返回的对象
• NavigableString对象，即指HTML中的文本节点
• comment对象，指HTML中的注释，如<!--like this one-->

2. findAll()与find()函数

用法：
findAll(tag, attributes, recursive, text, limit, keywords)
find(tag, attributes, recursive, text, keywords)

from urllib.request import urlopen
from bs4 import BeautifulSoup

html = urlopen("http://www.pythonscraping.com/pages/warandpeace.html")
bsObj = BeautifulSoup(html.read(),"html.parser")

nameList = bsObj.findAll("span",{"class":"green"})
for name in nameList:
    print(name.get_text())

Anna
Pavlovna Scherer
Empress Marya
Fedorovna
Prince Vasili Kuragin
Anna Pavlovna
St. Petersburg
the prince
Anna Pavlovna
Anna Pavlovna
the prince
the prince
the prince
Prince Vasili
Anna Pavlovna
Anna Pavlovna
the prince
Wintzingerode
King of Prussia
le Vicomte de Mortemart
Montmorencys
Rohans
Abbe Morio
the Emperor
the prince
Prince Vasili
Dowager Empress Marya Fedorovna
the baron
Anna Pavlovna
the Empress
the Empress
Anna Pavlovna's
Her Majesty
Baron
Funke
The prince
Anna
Pavlovna
the Empress
The prince
Anatole
the prince
The prince
Anna
Pavlovna
Anna Pavlovna

3.子节点、后代节点、兄弟节点、父节点

.children：获取该节点的所有字节点
.descendants：获取该节点的所有后代节点，包括字节点
.next_siblings：获取兄弟节点(除了自己，而且是后面的兄弟节点)
.previous_siblings：获取兄弟节点(除了自己，而且是后面的兄弟节点)
.next_sibling：获取后一个兄弟节点
.previous_sibling：获取前一个兄弟节点
.parents：获取所有父节点
.parent：获取第一级父节点

from urllib.request import urlopen
from bs4 import BeautifulSoup

html = urlopen("http://www.pythonscraping.com/pages/page3.html")
bsObj = BeautifulSoup(html.read(),"lxml")

#for child in bsObj.find("table",{"id":"giftList"}).children:
#for child in bsObj.find("table",{"id":"giftList"}).descendants:
for child in bsObj.find("table",{"id":"giftList"}).tr.next_siblings:
    print(child)
    
print(bsObj.find("img",{"src":"../img/gifts/img1.jpg"}).parent.previous_sibling.get_text())

<tr class="gift" id="gift1"><td>
Vegetable Basket
</td><td>
This vegetable basket is the perfect gift for your health conscious (or overweight) friends!
<span class="excitingNote">Now with super-colorful bell peppers!</span>
</td><td>
$15.00
</td><td>
<img src="../img/gifts/img1.jpg"/>
</td></tr>


<tr class="gift" id="gift2"><td>
Russian Nesting Dolls
</td><td>
Hand-painted by trained monkeys, these exquisite dolls are priceless! And by "priceless," we mean "extremely expensive"! <span class="excitingNote">8 entire dolls per set! Octuple the presents!</span>
</td><td>
$10,000.52
</td><td>
<img src="../img/gifts/img2.jpg"/>
</td></tr>


<tr class="gift" id="gift3"><td>
Fish Painting
</td><td>
If something seems fishy about this painting, it's because it's a fish! <span class="excitingNote">Also hand-painted by trained monkeys!</span>
</td><td>
$10,005.00
</td><td>
<img src="../img/gifts/img3.jpg"/>
</td></tr>


<tr class="gift" id="gift4"><td>
Dead Parrot
</td><td>
This is an ex-parrot! <span class="excitingNote">Or maybe he's only resting?</span>
</td><td>
$0.50
</td><td>
<img src="../img/gifts/img4.jpg"/>
</td></tr>


<tr class="gift" id="gift5"><td>
Mystery Box
</td><td>
If you love suprises, this mystery box is for you! Do not place on light-colored surfaces. May cause oil staining. <span class="excitingNote">Keep your friends guessing!</span>
</td><td>
$1.50
</td><td>
<img src="../img/gifts/img6.jpg"/>
</td></tr>



$15.00

4.正则

from urllib.request import urlopen
from bs4 import BeautifulSoup
import re

html = urlopen("http://www.pythonscraping.com/pages/page3.html")
bsObj = BeautifulSoup(html,"html.parser")

for img in bsObj.findAll("img",{"src":re.compile("\.\./img/gifts/img\d+\.jpg")}):
    print(img)

<img src="../img/gifts/img1.jpg"/>
<img src="../img/gifts/img2.jpg"/>
<img src="../img/gifts/img3.jpg"/>
<img src="../img/gifts/img4.jpg"/>
<img src="../img/gifts/img6.jpg"/>

5.匿名函数

from urllib.request import urlopen
from bs4 import BeautifulSoup
import re

html = urlopen("http://www.pythonscraping.com/pages/page3.html")
bsObj = BeautifulSoup(html,"html.parser")

#找出只有2个属性值的标签
for lst in bsObj.findAll(lambda tag: len(tag.attrs) == 2):
    print(lst)

<img src="../img/gifts/logo.jpg" style="float:left;"/>
<tr class="gift" id="gift1"><td>
Vegetable Basket
</td><td>
This vegetable basket is the perfect gift for your health conscious (or overweight) friends!
<span class="excitingNote">Now with super-colorful bell peppers!</span>
</td><td>
$15.00
</td><td>
<img src="../img/gifts/img1.jpg"/>
</td></tr>
<tr class="gift" id="gift2"><td>
Russian Nesting Dolls
</td><td>
Hand-painted by trained monkeys, these exquisite dolls are priceless! And by "priceless," we mean "extremely expensive"! <span class="excitingNote">8 entire dolls per set! Octuple the presents!</span>
</td><td>
$10,000.52
</td><td>
<img src="../img/gifts/img2.jpg"/>
</td></tr>
<tr class="gift" id="gift3"><td>
Fish Painting
</td><td>
If something seems fishy about this painting, it's because it's a fish! <span class="excitingNote">Also hand-painted by trained monkeys!</span>
</td><td>
$10,005.00
</td><td>
<img src="../img/gifts/img3.jpg"/>
</td></tr>
<tr class="gift" id="gift4"><td>
Dead Parrot
</td><td>
This is an ex-parrot! <span class="excitingNote">Or maybe he's only resting?</span>
</td><td>
$0.50
</td><td>
<img src="../img/gifts/img4.jpg"/>
</td></tr>
<tr class="gift" id="gift5"><td>
Mystery Box
</td><td>
If you love suprises, this mystery box is for you! Do not place on light-colored surfaces. May cause oil staining. <span class="excitingNote">Keep your friends guessing!</span>
</td><td>
$1.50
</td><td>
<img src="../img/gifts/img6.jpg"/>
</td></tr>