聚焦爬虫
过滤爬取到的数据,取出想要的部分
聚焦爬虫:爬取页面中指定的页面内容
-
编码流程
- 指定url
- 发起请求
- 获取响应数据
- 数据解析
- 持久化存储
-
数据解析分类
- 正则表达式
- bs4
- xpath (*)
数据解析原理 - 解析的局部文本内容都会在标签之间或标签的属性中存储 - 1. 进行标签的定位 - 2. 标签或者标签对应的属性中存储的数据值进行提取(即解析~~)
正则表达式爬取¶
import os
import requests
import re
# UA伪装
UA = 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/84.0.4147.89 Safari/537.36 Edg/84.0.522.44'
header = {'User-Agent': UA}
# 存储目录
folder = './qiushi'
if not os.path.exists(folder):
os.mkdir(folder)
def main():
# 分页处理
for i in range(1, 3):
url = f"https://www.qiushibaike.com/imgrank/page/{i}/"
# 1. 爬取整张页面
page_text = requests.get(url=url, headers=header).text
# 2. 使用聚焦爬虫进行数据解析
images = data_parse(page_text)
length = len(images) # 进度条所需
for index, image in enumerate(images):
# 3. 发起请求并获得数据
image_content = requests.get(url=image, headers=header).content
# 4. 持久化存储
image_name = image.split('/')[-1]
image_path = os.path.join(folder, image_name)
with open(image_path, 'wb') as f:
f.write(image_content)
# 进度打印
print(image_name + ' 下载成功!')
print(f'{index} / {length}', end='\r')
print(str(i) + "/ 2 page")
def data_parse(page_text):
""" 解析出每张图片的url """
# 分析网页后整理出正则表达式
ex = r'<div class="thumb">.*?<img src="(.*?)" alt.*?></div>'
images = re.findall(ex, page_text, re.S)
images = ['https:' + x for x in images] # 解析出来没有协议头,给增加上
return images
if __name__ == "__main__":
main()
--------------------------------------------------
# Output:
K7EUFEUIV3QY37P1.jpg 下载成功!
DFIAAL32X5J35JP2.jpg 下载成功!
...
NXUA4X1CMQP22UPP.jpg 下载成功!
FQILIKXCVMUIRXL8.jpg 下载成功!
1/ 2 page
95GRCYEUZANQ361J.jpg 下载成功!
2SXBFKSSK3JD3G2M.jpg 下载成功!
...
5YTNS4JH0PLZAO58.jpg 下载成功!
59CN77YAL198SM6M.jpg 下载成功!
2/ 2 page
示例网页¶
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>测试bs4</title>
</head>
<body>
<div>
<p>百里守约</p>
</div>
<div class="song">
<p>李清照</p>
<p>王安石</p>
<p>苏轼</p>
<p>柳宗元</p>
<a href="https://www.song.com" title="赵匡胤" target="_self">
<span>this is span</span>
宋朝是最强大的王朝,不是军队的强大,而是经济很强大,国民都很有钱
</a>
<a href="" class="du">总为浮云能避日,长安不见使人愁</a>
<img src="https://www.baidu.com/meinv.jpg" alt="">
</div>
<div class="tang">
<ul>
<li><a href="https://www.baidu.com" title="qing">清明时节雨纷纷,路上行人欲断魂。借问酒家何处有,牧童遥指杏花村。</a></li>
<li><a href="https://www.163.com" title="qin">秦时明月汉时光,万里长征人未还。但使龙城飞将在,不教胡马度阴山。</a></li>
<li><a href="https://www.126.com" alt="qi">岐王宅里寻常见,崔久堂前几度闻。正是江南好风景,落花时节又逢君。</a></li>
<li><a href="https://www.sina.com" class="du">杜甫</a></li>
<li><a href="https://www.dudu.com" class="du">杜牧</a></li>
<li><b>杜小月</b></li>
<li><i>度蜜月</i></li>
<li><a href="https://www.haha.com" id="feng">凤凰台上凤凰游,凤去台空江自流。吴宫花草埋幽径,晋代衣冠成古丘。</a></li>
</ul>
</div>
</body>
</html>
以下爬虫示例均以此网页示例为基础 有点丑,将就一下。
bs4爬取¶
安装¶
win 下: >_ pip install bs4 >_ pip install lxml
Linux 下: >_ pip install Beautifulsoup4
导入¶
from bs4 import BeautifulSoup
使用¶
- 创建bs对象并传入待解析对象
- 传入待解析对象为本地文件
- 传入待解析对象为网络请求
定位数据¶
方法 | 用 | 返值 |
---|---|---|
tagName | 返回首tagName标签 | bs4.element.Tag |
find('tagName') | 返回首tagName标签 | bs4.element.Tag |
find('tagName', class_/id/attrName='value') | 返回首属性为value的tagName标签 | bs4.element.Tag |
find_all('tagName') | 返回所符合要求的标签 | bs4.element.ResultSet |
select(['selector' + ]'tagName') | 通过CS选择器+标签名定位标签,返回多个 | bs4.element.ResultSet |
select_one(['selector' + ]'tagName') | 通过CS选择器+标签名定位标签,返回一个 | bs4.element.Tag |
bs.tagName¶
bs.tagName
:返回文档中**第一次**出现tagName对应的标签with open('./bs_test.html', 'r', encoding='utf-8') as f: bs = BeautifulSoup(f, 'lxml') # 创建bs对象 tag_a = bs.a # 定位数据 print(tag_a) print(type(tag_a)) # <class 'bs4.element.Tag'> -------------------------------------------------- # Output: <a href="https://www.song.com" target="_self" title="赵匡胤"> <span>this is span</span> 宋朝是最强大的王朝,不是军队的强大,而是经济很强大,国民都很有钱 </a> <class 'bs4.element.Tag'>
bs.find()¶
bs.find()
:find('tagName')
:等同于 bs.tagNamewith open('./bs_test.html', 'r', encoding='utf-8') as f: bs = BeautifulSoup(f, 'lxml') # 创建bs对象 tag_div = bs.find('div') # 定位数据 print(tag_div) print(type(tag_div)) # <class 'bs4.element.Tag'> -------------------------------------------------- # Output: <div> <p>百里守约</p> </div> <class 'bs4.element.Tag'>
find('tagName', class_/is/attrName='value')
:通过限定属性来定位标签with open('./bs_test.html', 'r', encoding='utf-8') as f: bs = BeautifulSoup(f, 'lxml') # 创建bs对象 tag_a = bs.find('a', class_='du') # 定位数据 print(tag_a) print(type(tag_a)) # <class 'bs4.element.Tag'> -------------------------------------------------- # Output: <a class="du" href="">总为浮云能避日,长安不见使人愁</a> <class 'bs4.element.Tag'>
bs.find_all('tagName')
:返回复合要求的所有标签(集合)with open('./bs_test.html', 'r', encoding='utf-8') as f: bs = BeautifulSoup(f, 'lxml') # 创建bs对象 tag_p = bs.find_all('p') # 定位数据 print(tag_p) print(type(tag_p)) # <class 'bs4.element.ResultSet'> -------------------------------------------------- # Output: [<p>百里守约</p>, <p>李清照</p>, <p>王安石</p>, <p>苏轼</p>, <p>柳宗元</p>]
bs.select()¶
bs.select('selector' + 'tagName')
:可以通过**CSS择器+标签名**定位,包括层级选择器、标签选择器等with open('./bs_test.html', 'r', encoding='utf-8') as f: bs = BeautifulSoup(f, 'lxml') # 创建bs对象 tag_div = bs.select('#feng') # 定位数据 print(tag_div) print(type(tag_div)) # <class 'bs4.element.ResultSet'> -------------------------------------------------- # Output: [<a href="https://www.haha.com" id="feng">凤凰台上凤凰游,凤去台空江自流。吴宫花草埋幽径,晋代衣冠成古丘。</a>] <class 'bs4.element.ResultSet'>
with open('./bs_test.html', 'r', encoding='utf-8') as f: bs = BeautifulSoup(f, 'lxml') # 创建bs对象 tag1_a = bs.select('.tang > ul > li > a') # 定位数据 tag2_a = bs.select('.tang >ul a') # 定位数据 print(tag1_a) print(tag2_a) print(type(tag1_a)) # <class 'bs4.element.ResultSet'> -------------------------------------------------- # Output: [<a href="https://www.baidu.com" title="qing">清明时节雨纷纷,路上行人欲断魂。借问酒家何处有,牧童遥指杏花村。</a>, <a href="https://www.163.com" title="qin">秦时明月汉时光,万里长征人未还。但使龙城飞将在,不教胡马度阴山。</a>, <a alt="qi" href="https://www.126.com">岐王宅里寻常见,崔久堂前几度闻。正是江南好风景,落花时节又逢君。</a>, <a class="du" href="https://www.sina.com">杜甫</a>, <a class="du" href="https://www.dudu.com">杜牧</a>, <a href="https://www.haha.com" id="feng">凤凰台上凤凰游,凤去台空江自流。吴宫花草埋幽径,晋代衣冠成古丘。</a>] [<a href="https://www.baidu.com" title="qing">清明时节雨纷纷,路上行人欲断魂。借问酒家何处有,牧童遥指杏花村。</a>, <a href="https://www.163.com" title="qin">秦时明月汉时光,万里长征人未还。但使龙城飞将在,不教胡马度阴山。</a>, <a alt="qi" href="https://www.126.com">岐王宅里寻常见,崔久堂前几度闻。正是江南好风景,落花时节又逢君。</a>, <a class="du" href="https://www.sina.com">杜甫</a>, <a class="du" href="https://www.dudu.com">杜牧</a>, <a href="https://www.haha.com" id="feng">凤凰台上凤凰游,凤去台空江自流。吴宫花草埋幽径,晋代衣冠成古丘。</a>] <class 'bs4.element.ResultSet'>
with open('./bs_test.html', 'r', encoding='utf-8') as f: bs = BeautifulSoup(f, 'lxml') # 创建bs对象 tag_div = bs.select_one('.du') # 定位数据 print(tag_div) print(type(tag_div)) # <class 'bs4.element.Tag'> -------------------------------------------------- # Output: <a class="du" href="">总为浮云能避日,长安不见使人愁</a> <class 'bs4.element.Tag'>
解析数据¶
方法 | 用 | 返值 |
---|---|---|
.text | 返回标签下所有**直系和非直系标签**的所有本 | str |
.get_text() | 返回标签下所有**直系和非直系标签**的所有本 | str |
.string | 返回标签下所有**直系标签**的所有本 | bs4.element.NavigableString |
获取文本¶
bs.tagName.text/string/get_text()
:获取标签之间的*所有文本**text/get_text()
:可以获取标签下**直系和非直系**的所有文本string
:只能获取标签下**直系**的文本,没有返回 Nonewith open('./bs_test.html', 'r', encoding='utf-8') as f: bs = BeautifulSoup(f, 'lxml') # 创建bs对象 txt_li = bs.find('li').string print(txt_li) print(type(txt_li)) # <class 'bs4.element.NavigableString'> -------------------------------------------------- # Output: 清明时节雨纷纷,路上行人欲断魂。借问酒家何处有,牧童遥指杏花村。 <class 'bs4.element.NavigableString'>
获取属性¶
bs.tagName['attrName']
:获取标签中的**属性内容**
案例¶
从诗词名句网下载一整部《论语》
import time
import requests
import os
from bs4 import BeautifulSoup
UA = 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/84.0.4147.89 Safari/537.36 Edg/84.0.522.44'
header = {'User-Agent': UA}
folder = '.\\爬虫\\论语'
if not os.path.exists(folder):
os.mkdir(folder)
def req_catalog(url):
""" 请求目录列表 """
return requests.get(url=url, headers=header).text
def catalog_parse(res_text):
""" 解析目录列表 """
bs = BeautifulSoup(res_text, 'lxml')
links = bs.select('.book-mulu > ul > li > a')
catalog_list = [[x.string, x['href']] for x in links]
return catalog_list
def download_content(catalog_list):
""" 请求内容页 """
url = 'https://www.shicimingju.com'
length = len(catalog_list)
for index, elem in enumerate(catalog_list):
# 请求数据
content_text = requests.get(url=url + elem[1], headers=header).text
# 解析数据
content = contents_parse(content_text)
# 持久化存储
filename = str(index + 1) + '-' + elem[0] + '.txt'
filepath = os.path.join(folder, filename)
with open(filepath, 'w', encoding='utf-8') as f:
f.write(content)
print("已下载:" + str(index + 1) + " / " + str(length), end="\r")
return 1
def contents_parse(page_text):
""" 解析内容 """
bs = BeautifulSoup(page_text, 'lxml')
contents = bs.select('.chapter_content > p') # 取出所有p标签
texts = [x.string for x in contents] # 取出内容,过滤掉P标签
content = ''
for i in texts:
content += str(i)
return content
def main():
url = "https://www.shicimingju.com/book/lunyu.html"
catalog_list = list()
try:
catalog_text = req_catalog(url)
catalog_list = catalog_parse(catalog_text)
print("下载成功!") if download_content(catalog_list) else print("下载失败")
except TimeoutError:
print("TimeoutError\n")
time.sleep(2)
print("下载成功!") if download_content(catalog_list) else print("下载失败")
except Exception:
print("Exception\n")
if __name__ == '__main__':
main()
xpath爬取¶
最常用、通用性最强的,最便捷高效的一种解析方式。
解析步骤¶
- 实例化一个etree对象,并且需要将被解析的页面源码数据加载到该对象中。
- 通过调用etree对象中的xpath方法结合着xpath表达式实现标签的定位和内容的捕获
- xpath定位到数据后返回的不是数据的内容,而已一个列表,里面放置了解析出来的**Element对象**
安装¶
>_: pip install lxml
导入¶
from lxml import etree
使用¶
- 创建etree对象并传入待解析对象
- 传入待解析对象为本地文件
tree = etree.parse(filePath)
- 传入待解析对象为网络请求
tree = etree.HTML('page_text')
- 传入待解析对象为本地文件
-
定位数据:
tree.xpath(xpath表达式)
在XPath中有7种节点:元素、属性、文本、文档、命名空间、处理指令、注释。 元素、属性、文本 为常用节点。expression description nodeName 选择nodeName节点的所有子节点 / 从根节点或/前的节点开始,不跨层级匹配 // 从//前的节点开始,跨层级匹配 . 选择当前节点 .. 选择当前节点的父节点 @ 匹配元素属性 * 匹配所有节点 @* 匹配节点所有属性 [] 按索引定位 -
/
:表示从根节点开始定位 > / 放在最前面的时候表示根节点,不是放在最前面的时候表示2.from lxml import etree with open('./test.html', 'r', encoding='utf-8') as f: f_content = f.read() tree = etree.HTML(f_content) r = tree.xpath('/html/body/div/p') print(r) print(type(r)) -------------------------------------------------- xpath 在匹配的时候是贪婪的,示例中有两个 div 下都有 p,所以匹配到了5个 # Output: [<Element p at 0x252e2de8780>, <Element p at 0x252e2de87c0>, <Element p at 0x252e2de8800>, <Element p at 0x252e2de8840>, <Element p at 0x252e2de8880>] <class 'list'>
//
:表示匹配多级/a/b//c,就表示匹配 a 标签下的 b 标签下所有c标签
3.from lxml import etree with open('./test.html', 'r', encoding='utf-8') as f: f_content = f.read() tree = etree.HTML(f_content) r = tree.xpath('/html//a') # 等价于 r = tree.xpath('//a') print(r) print(type(r)) -------------------------------------------------- html节点下总共有8个a标签,所以匹配到8个element对象 # Output: [<Element a at 0x1e5f55e9680>, <Element a at 0x1e5f55e96c0>, <Element a at 0x1e5f55e9700>, <Element a at 0x1e5f55e9740>, <Element a at 0x1e5f55e9780>, <Element a at 0x1e5f55e9800>, <Element a at 0x1e5f55e9840>, <Element a at 0x1e5f55e9880>] <class 'list'>
@
:表示通过属性定位tag[@attrName="attrValue"]
@后面加上属性名,比如class、id、href、src等等4.from lxml import etree with open('./test.html', 'r', encoding='utf-8') as f: f_content = f.read() tree = etree.HTML(f_content) r = tree.xpath('/html//div[@class="song"]') print(r) print(type(r)) -------------------------------------------------- html节点下总共有8个a标签,所以匹配到8个element对象 # Output: [<Element div at 0x24d64839640>] <class 'list'>
[]
:表示通过索引定位tag[index]
这里是索引是**从1开始的**5.from lxml import etree with open('./test.html', 'r', encoding='utf-8') as f: f_content = f.read() tree = etree.HTML(f_content) print(tree.xpath('/html//div[@class="song"]/p[1]')) print(tree.xpath('/html//div[@class="song"]/p[1]/text()')) print(tree.xpath('/html//div[@class="song"]/p[2]')) print(tree.xpath('/html//div[@class="song"]/p[3]')) -------------------------------------------------- 这里的下标是从1开始的 # Output: [<Element p at 0x1df3d4395c0>] ['李清照'] [<Element p at 0x1df3d439580>] [<Element p at 0x1df3d439600>] <class 'list'>
/text()
:返回标签之间的文本,取文本tag/text()
:获取tag下**直系**的文本tag//text()
:获取tag下**直系和非直系**的文本5.from lxml import etree with open('./test.html', 'r', encoding='utf-8') as f: f_content = f.read() tree = etree.HTML(f_content) r1 = tree.xpath('/html//div[@class="song"]/p[3]') r2 = tree.xpath('/html//div[@class="song"]/p[3]/text()') r3 = tree.xpath('/html//div[@class="song"]/p[3]/text()')[0] print(r1) print(r2) print(r3) -------------------------------------------------- # Output: [<Element p at 0x1d4e4c29540>] ['苏轼'] 苏轼 <class 'list'>
/@attrName
:返回标签的attrName属性的值tag/@attrName
:获取tag标签中的attrName属性的值5.from lxml import etree with open('./test.html', 'r', encoding='utf-8') as f: f_content = f.read() tree = etree.HTML(f_content) r1 = tree.xpath('//div[@class="song"]/a/@href') print(r1) r2 = tree.xpath('//div[@class="song"]/img/@src') print(r2) -------------------------------------------------- # Output: ['https://www.song.com', ''] ['https://www.baidu.com/meinv.jpg'] <class 'list'>
/@*
:返回标签的所有属性的值tag/@*
:获取tag标签中的所有属性的值from lxml import etree with open('./test.html', 'r', encoding='utf-8') as f: f_content = f.read() tree = etree.HTML(f_content) r1 = tree.xpath('//div[@class="song"]/a[@target="_self"]/@*') print(r1) -------------------------------------------------- # Output: ['https://www.song.com', '赵匡胤', '_self'] <class 'list'>
-
案例¶
从彼岸图网下载4K图保存至本地
import os
from lxml import etree
import requests
UA = 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/84.0.4147.89 Safari/537.36 Edg/84.0.522.44'
header = {'User-Agent': UA}
path = './爬虫/4k'
if not os.path.exists(path):
os.mkdir(path)
def get_url():
""" 获取所有图片地址 """
url = 'http://pic.netbian.com/4kmeinv/'
index_text = requests.get(url=url, headers=header).text
tree = etree.HTML(index_text)
a_list = tree.xpath('//div[@id="main"]/div[3]/ul/li/a')
# response.encoding = 'utf-8' # 处理中文乱码方式1,不一定有效
img_list = list()
for a in a_list:
src: str = 'http://pic.netbian.com' + a.xpath('./@href')[0]
title: str = a.xpath('./b/text()')[0] + '.jpg'
title = title.encode('iso-8859-1').decode('gbk') # 处理中文乱码方式2
img_list.append((title, src))
return img_list
def download_img(img_info):
""" 下载图片 """
img_content = requests.get(url=img_info[1], headers=header).content
filepath = os.path.join(path, img_info[0])
with open(filepath, 'wb') as f:
f.write(img_content)
def main():
img_list = get_url()
for img_info in img_list:
download_img(img_info)
if __name__ == '__main__':
main()