[Python]BS4 与 一个KDS 美图爬虫

BS4

BeautifulSoup是用来从HTML or XML中提取数据的Python lib。BeautifulSoup将文档转化为树形结构(DOM),每个节点都是下述四种类型的Python对象:

  1. BeautifulSoup
  2. Tag
  3. NavigableString
  4. Comment

从集合角度理解以上4中类的关系(类概念上并不准确)

  • BeautifulSoup 为全集(将Document以入参传入生成BeautifulSoup object), 包含 Tag子集
  • Tag 包含 NavigableString 子集
  • Comment 为 NavigableString 特殊集合

Usage

BeautifulSoup的第一个入参是Document,第二个入参指定Document parser 类型.

from bs4 import BeautifulSoup
import requests, re

url = 'http://m.kdslife.com/club/'
# get whole HTTP response
response = requests.get(url)
# args[0] is HTML document, args[1] select LXML parser. returned BeautifulSoup object
soup = BeautifulSoup( response.text, 'lxml')
print soup.name
# [document]'
print type(soup)
# 

Sample codes for Tag objects

# BeutifulSoup --> Tag 
# get the Tag object(title)
res = soup.title
print res
# KDS Life

res = soup.title.name
print res
# title

# attribules of a Tag object
res = soup.section
print type(res)
# 

print res['class']
# ['forum-head-hot', 'clearfix']

# All the attributes of section Tag object, returned a dict
print res.attrs
#{'class': ['forum-head-hot', 'clearfix']}

Sample codes for NavigableString object

# NavigableString object describes the string in Tag object
res = soup.title
print res.string
# KDS Life
print type(res.string)
# <class 'bs4.element.NavigableString'>

Sample codes for Comment object

# Comment, is a special NavigableString object
markup = "<b>b>"
soup = BeautifulSoup(markup)
comment = soup.b.string
print type(comment)
# <class 'bs4.element.Comment'>

BS4 Parser

按照优先顺序自动解析,’lxml’ –> ‘html5lib’ –> ‘html.parser’


常用Tag对象方法

find_all()

find_all(name,attrs,recursive,text,**kwargs) 不解释,直接看代码

# filter, returned a matching list
# returned [] if matching nothing
title = soup.find_all('title')
print title
#[Google]

res = soup.find_all('div', 'topAd')
print res

# find all the elements whose id is 'gb-main'
res = soup.find_all(id='topAd')
print res
#[
...
]
# find all the elements with 'img' tag and 'src' attribute matching the specific pattern res = soup.find_all('img', src=re.compile(r'^http://club-img',re.I)) print res # [, #...]

select()

# css selector
# select those whose tag's id = wrapperto
res = soup.select('#wrapperto')
print res
# [
"swiper-wrapper clearfix" id="wrapperto">
] # select those 'img' tags who have 'src' attribute res = soup.select('img[src]') print res #[<span"" src="http://icon.pch-img.net/kds/club_m/club/icon/user1.png"/>, "http://club-img.kdslife.com/attach/1k0/gs/a/o41gty-1coa.png@0o_1l_600w_90q.src"/>] # select those 'img' tags whose 'src' attribute is res = soup.select('img[src=http://icon.pch-img.net/kds/club_m/club/icon/user1.png]') print res # [<span"" src="http://icon.pch-img.net/kds/club_m/club/icon/user1.png"/>]

Other

# get_text()
markup = '\n a link to example.com\n'
soup = BeautifulSoup(markup,'lxml')
res = soup.get_text()
print res
#  a link to example.com

res = soup.i.get_text()
print res
# example.com

# .stripped_string
res = soup.stripped_strings
print list(res)
# [u'a link to', u'example.com']

最后贴上一个简单的KDS图片爬虫

A KDS image spider


Note

  • BeautifulSoup进行了编码检测并自动转为Unicode. soup.original_encoding属性来获取自动识别编码的结果。
  • Input converts to unicode, output encodes with utf-8
  • 在BS使用中,可配合 XPath expression使用

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