Of Stack

Python USES beautifulSoup to implement a crawler

  • 2020-04-02 14:13:10
  • OfStack

I've talked before about using phantomjs as a crawler to grab web pages with a selector

Using beautifulSoup (document: (link: http://www.crummy.com/software/BeautifulSoup/bs4/doc/)) this python module, you can easily grab web content 


# coding=utf-8
import urllib
from bs4 import BeautifulSoup

url ='http://www.baidu.com/s'
values ={'wd':' tennis '}
encoded_param = urllib.urlencode(values)
full_url = url +'?'+ encoded_param
response = urllib.urlopen(full_url)
soup =BeautifulSoup(response)
alinks = soup.find_all('a')

Above can grab baidu to search out the result is the record of tennis.

BeautifulSoup has a lot of very useful methods built into it.

A few handy features:

Construct a node element 



soup = BeautifulSoup('<b class="boldest">Extremely bold</b>')

tag = soup.b

type(tag)

# <class 'bs4.element.Tag'>

Properties can be obtained using attr, and the result is a dictionary 



tag.attrs

# {u'class': u'boldest'}

Or take the attribute of tag. Class directly.

Properties can also be manipulated freely 


tag['class'] = 'verybold'
tag['id'] = 1
tag
# <blockquote class="verybold" id="1">Extremely bold</blockquote>

del tag['class']
del tag['id']
tag
# <blockquote>Extremely bold</blockquote>

tag['class']
# KeyError: 'class'
print(tag.get('class'))
# None

You can also navigate around and find dom elements, as in the following example

1. Build a document 


html_doc = """
<html><head><title>The Dormouse's story</title></head>

<p><b>The Dormouse's story</b></p>

<p>Once upon a time there were three little sisters; and their names were
<a href="http://example.com/elsie" id="link1">Elsie</a>,
<a href="http://example.com/lacie" id="link2">Lacie</a> and
<a href="http://example.com/tillie" id="link3">Tillie</a>;
and they lived at the bottom of a well.</p>

<p>...</p>
"""

from bs4 import BeautifulSoup
soup = BeautifulSoup(html_doc)

2. All sorts of figure 


soup.head
# <head><title>The Dormouse's story</title></head>
soup.title
# <title>The Dormouse's story</title>
soup.body.b
# <b>The Dormouse's story</b>
soup.a
# <a class="sister" href="http://example.com/elsie" id="link1">Elsie</a>
soup.find_all('a')
# [<a class="sister" href="http://example.com/elsie" id="link1">Elsie</a>,
# <a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>,
# <a class="sister" href="http://example.com/tillie" id="link3">Tillie</a>]
head_tag = soup.head
head_tag
# <head><title>The Dormouse's story</title></head>

head_tag.contents
[<title>The Dormouse's story</title>]

title_tag = head_tag.contents[0]
title_tag
# <title>The Dormouse's story</title>
title_tag.contents
# [u'The Dormouse's story']
len(soup.contents)
# 1
soup.contents[0].name
# u'html'
text = title_tag.contents[0]
text.contents

for child in title_tag.children:
  print(child)
head_tag.contents
# [<title>The Dormouse's story</title>]
for child in head_tag.descendants:
  print(child)
# <title>The Dormouse's story</title>
# The Dormouse's story

len(list(soup.children))
# 1
len(list(soup.descendants))
# 25
title_tag.string
# u'The Dormouse's story'
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