标签：requests res 开始 多次 position 下载链接 爬取 head 链接
[TOC]
---
#### 1.图片下载
```Python
# 百度图片:http://image.baidu.com/
# 搜狗图片:https://pic.sogou.com/
```
```Python
# 图片爬取:
1).寻找图片下载的url: elements与network抓包
2).浏览器中访问url, 进行验证
3).编写代码获取url
4).请求url地址, 获取二进制流
5).将二进制流写入文件
```
```Python
# 百度图片:
import time
import requests
from lxml import etree
from selenium import webdriver
# 实例化浏览器对象
browser = webdriver.Chrome(‘./chromedriver.exe‘)
# 访问网页并操控网页元素获取搜索结果
browser.get(‘http://image.baidu.com/‘)
input_tag = browser.find_element_by_id(‘kw‘)
input_tag.send_keys(‘乔碧萝‘)
search_button = browser.find_element_by_class_name(‘s_search‘)
search_button.click()
# 通过js实现鼠标向下滚动, 获取更多页面源码
js = ‘window.scrollTo(0, document.body.scrollHeight)‘
for times in range(3):
browser.execute_script(js)
time.sleep(3)
html = browser.page_source
# 解析数据获取图片连接:
tree = etree.HTML(html)
url_list = tree.xpath(‘//div[@id="imgid"]/div/ul/li/@data-objurl‘)
for img_url in url_list:
headers = {
‘User-Agent‘: ‘Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/76.0.3809.132 Safari/537.36‘
}
content = requests.get(url=img_url, headers=headers).content
if ‘token‘ not in img_url:
with open(‘./baidupics/%s‘%img_url.split(‘/‘)[-1], ‘wb‘) as f:
f.write(content)
```
```Python
# 搜狗图片:
import requests
import re
url = ‘http://pic.sogou.com/pics?‘
params = {
‘query‘: ‘韩美娟‘
}
res = requests.get(url=url, params=params).text
url_list = re.findall(r‘,"(https://i\d+piccdn\.sogoucdn.com/.*?)"]‘, res)
for img_url in url_list:
headers = {
‘User-Agent‘: ‘Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/76.0.3809.132 Safari/537.36‘
}
print(img_url)
content = requests.get(url=img_url, headers=headers).content
name = img_url.split(‘/‘)[-1] + ‘.jpg‘
with open(‘./sougoupics/%s.jpg‘%name, ‘wb‘) as f:
f.write(content)
```
---
#### 2.JS动态渲染
```Python
1).selenium爬取: selenium测试框架, 完全模人操作浏览器, *** page_source ***
2).基础语法:
from selenium import webdriver
# 实例化浏览器对象:
browser = webdriver.Chrome(‘浏览器驱动路径‘) # 在当前路径下: ‘./chromedriver.exe‘
# 访问响应的url地址:
browser.get(url)
# 获取页面元素:
find_element_by_id
find_element_by_name(): name是标签的name属性值
find_element_by_class_name: class的属性值
find_element_by_xpath: 根据xpath表达式定位元素
find_element_by_css_selector:根据css选择器
# 示例:获取一个id为kw的input输入框
input_tag = browser.find_element_by_id(‘kw‘)
# 输入内容:
input_tag.clear()
input_tag.send_keys(‘乔碧萝殿下‘)
# 点击button按钮:
button.click()
# 执行JS代码:
js = ‘window.scrollTo(0, document.body.scrollHeight)‘
for i in range(3):
browser.execute_script(js)
# 获取HTML源码: 记住没有括号*****
html = browser.page_source # str类型
# 数据解析工作:
1).xpath提取数据:
2).正则提取: 正则表达式的书写 + re模块的使用
3).Beautifulsoup: CSS选择器 -->(节点选择器, 方法选择器, CSS选择器)
# 媒体类型: 视频, 图片, 压缩包, 软件安装包
1).下载链接
2).requests请求: response.content --> 二进制流
scrapy框架: response.body --> 二进制流
3).写文件:
with open(‘./jdkfj/name‘, ‘wb‘) as f:
f.write(res.content | response.body)
```
---
#### 3.数据解析
```Python
1.Xpath
# 编码流程
from lxml import etree
# 实例化etree对象
tree = etree.HTML(res.text)
# 调用xpath表达式提取数据
li_list = tree.xpath(‘xpath表达式‘) # xpath提取的数据在列表中
# 嵌套
for li in li_list:
li.xpath(‘xpath表达式‘)
# ./
# .//
# 基础语法:
./:从当前的根节点向下匹配
../:从当前节点下的任意位置匹配
nodeName: 节点名定位
nodename[@attributename="value"]: 根据属性定位
单属性多值匹配:contains--> div[contains(@class, "item")]
多属性匹配: and --> div[@class="item" and @name="divtag"]
@attributename: 提取其属性值
text(): 提取文本信息
# 按序选择:
1).索引定位: 索引从1开始, res.xpath(‘//div/ul/li[1]/text()‘): 定位第一个li标签
requests模块请求的响应对象:
res.text-->文本
res.json()-->python的基础数据类型 --> 字典
res.content--> 二进制流
2).last()函数定位: 最后一个, 倒数第二个:last()-1
res.xpath(‘//div/ul/li[last()]‘): 定位最后一个
res.xpath(‘//div/ul/li[last()-1]‘): 定位倒数第二个
3).position()函数: 位置
res.xpath(‘//div/ul/li[position()<4]‘)
2.BS4基础语法:
# 编码流程:
from bs4 import BeautifulSoup
# 实例化soup对象
soup = BeautifulSoup(res.text, ‘lxml‘)
# 定位节点
soup.select(‘CSS选择器‘)
# CSS选择器语法:
id: #
class: .
soup.select(‘div > ul > li‘) # 单层级选择器
soup.select(‘div li‘) # 多层级选择器
# 获取节点的属性或文本:
tag.string: 取直接文本 --> 当标签中除了字节文本, 还包含其他标签时, 取不到直接文本
tag.get_text(): 取文本
tag[‘attributename‘]: 取属性(试试属性有两个(包含)值以上时返回的数据类型)
3.正则 & re模块
分组 & 非贪婪匹配:() --> ‘dfkjd(kdf.*?dfdf)dfdf‘
<a href="https://www.baidu.com/kdjfkdjf.jpg">这是一个a标签</a> -->
‘<a href="(https://www.baidu.com/.*?\.jpg)">‘
量词:
+ : 匹配1次或多次
* : 匹配0次获取多次
{m}: 匹配m次
{m,n}: 匹配m到n次
{m,}: 至少m次
{,n}: 至多n次
re模块:
re.findall(‘正则表示‘, res.text) --> list列表
```
---
#### 4.持久化存储
```Python
1.txt
############# 写入txt文件 ###############
if title and joke and comment:
# with open(‘qbtxt.txt‘, ‘a‘, encoding=‘utf-8‘) as txtfile:
# txtfile.write(‘&‘.join([title[0], joke[0], comment[0]]))
# txtfile.write(‘\n‘)
# txtfile.write(‘********************************************\n‘)
2.json
############# 写入json文件 ################
# dic = {‘title‘: title[0], ‘joke‘:joke[0], ‘comment‘:comment[0]}
# with open(‘jsnfile.json‘, ‘a‘, encoding=‘utf-8‘) as jsonfile:
# jsonfile.write(json.dumps(dic, indent=4, ensure_ascii=False))
# jsonfile.write(‘,‘+‘\n‘)
3.csv
############# 写入CSV文件 ##################
with open(‘csvfile.csv‘, ‘a‘, encoding=‘utf-8‘) as csvfile:
writer = csv.writer(csvfile, delimiter=‘ ‘)
writer.writerow([title[0], joke[0], comment[0]])
############# scrapy框架 ##################
FEED_URI = ‘file:///home/eli/Desktop/qtw.csv‘
FEED_FORMAT = ‘CSV‘
4.mongodb
import Pymongo
# 管道类 class MongoPipeline(object):
# 初始化方法, __new__: 构造方法, 在内存中开辟一块空间
def __init__(self, mongo_uri, mongo_db):
self.mongo_uri = mongo_uri
self.mongo_db = mongo_db
@classmethod
def from_crawler(cls, crawler):
return cls(
mongo_uri = crawler.settings.get(‘MONGO_URI‘),
mongo_db = crawler.settings.get(‘MONGO_DB‘)
)
def open_spider(self, spider):
self.client = pymongo.MongoClient(self.mongo_uri)
self.db = self.client[self.mongo_db]
def process_item(self, item, spider):
self.db[‘news‘].insert(dict(item))
# 在一个项目中可能存在多个管道类, 如果该管道类后面还有管道类需要存储数据, 必须return item
return item
def close_spider(self, spider):
self.client.close()
5.mysql
import pymysql
def MysqlPipeline(object):
def __init__(self, host, database, user, password, port):
self.host = host
self.database = database
self.user = user
self.password = password
self.port = port
@classmethod
def from_crawler(self, crawler):
return cls(
host = crawler.settings.get(‘MYSQL_HOST‘)
database = crawler.settings.get(‘MYSQL_DATABASE‘)
user = crawler.settings.get(‘MYSQL_USER‘)
password= crawler.settings.get(‘MYSQL_PASSWORD‘)
port = crawler.settings.get(‘MYSQL_PORT‘)
)
def open_spider(self, spider):
self.db = pymysql.connect(self.host, self.user, self.password, self.database, charset=‘utf-8‘, port=self.port)
self.cursor = self.db.cursor()
```
---
标签：requests res 开始 多次 position 下载链接 爬取 head 链接
原文地址：https://www.cnblogs.com/hanghaiwang/p/11531411.html
