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图片懒加载和UA池,UA代理池

1,动态数据加载的处理

图片懒加载概念:
- 图片懒加载是一种页面优化技术.图片作为一种网络资源,在被请求时也与静态资源一样,将占用网络资源,而一次性将整个页面的所有图片加载完,将大大增加页面首屏加载时间,为了解决这些问题,通过前后端配合,是图片仅在浏览器当前窗口出现时才加载给图片,达到减少首屏图片请求数的技术叫做"图片懒加载"
网站一般如何实现图片懒记载技术?
- 在网页源码中,img标签中首先会使用一个"伪属性"(通常使用src2,original......)去存放真正的图片连接,而并非是直接存放在src属性中,当图片出现到页面的可视化区域中,会动态将伪属性替换成src属性,完成图片的记载

2,selenium

什么是selenium:是Python的一个第三方库,对外提供的接口可以操作浏览器,然后让浏览器完成自动化的操作
环境搭建:
- 安装selenium: pip install selenium
- 获取某一款浏览器的驱动程序(以谷歌浏览器为例)
- 谷歌浏览器下载驱动地址: http://chromedriver.storage.googleapis.com/index.html
- 下载驱动程序必须和浏览器的版本统一,大家可以根据以下版本对照下载:
- http://blog.csdn.net/huilan_same/article/details/51896672
效果展示:

from selenium import webdriver
from time import sleep

# 后面是你的浏览器驱动位置，记得前面加r'','r'是防止字符转义的
driver = webdriver.Chrome(r'驱动程序路径')
# 用get打开百度页面
driver.get("http://www.baidu.com")
# 查找页面的“设置”选项，并进行点击
driver.find_elements_by_link_text('设置')[0].click()
sleep(2)
# # 打开设置后找到“搜索设置”选项，设置为每页显示50条
driver.find_elements_by_link_text('搜索设置')[0].click()
sleep(2)

# 选中每页显示50条
m = driver.find_element_by_id('nr')
sleep(2)
m.find_element_by_xpath('//*[@id="nr"]/option[3]').click()
m.find_element_by_xpath('.//option[3]').click()
sleep(2)

# 点击保存设置
driver.find_elements_by_class_name("prefpanelgo")[0].click()
sleep(2)

# 处理弹出的警告页面   确定accept() 和 取消dismiss()
driver.switch_to_alert().accept()
sleep(2)
# 找到百度的输入框，并输入 美女
driver.find_element_by_id('kw').send_keys('美女')
sleep(2)
# 点击搜索按钮
driver.find_element_by_id('su').click()
sleep(2)
# 在打开的页面中找到“Selenium - 开源中国社区”，并打开这个页面
driver.find_elements_by_link_text('美女_百度图片')[0].click()
sleep(3)

# 关闭浏览器
driver.quit()

代码详解:

导包: from selenium import webdriver
创建浏览器对象,通过该浏览器对象可以操作浏览器:browser = webdriver.Chrome("驱动路径")
使用浏览器发起指定请求
browser.get(url)
使用下面方法,查找指定的元素进行操作
1. find_element_by_id 根据id中节点
2. find_elements_by_name 根据name找
3. find_elements_by_xpath 根据xpath查找
4. find_elements_by_yag_name 根据标签名查找
5. find_elements_by_calss_name 根据class名字查找

3,phantomJS

phantomJS是一款无界面的浏览器,其自动化操作流程和上述操作胡歌浏览器是一致的,有于是无界面的,为了能够展示自动化操作流程,phantomJS为用户提供了一个截屏功能,使用save_screenshot实现

from selenium import webdriver
import time

bro = webdriver.PhantomJS(executable_path="D:PhantomJSphantomjs-2.1.1-windowsinphantomjs.exe")
# 请求的发送

bro.get(url="https://www.baidu.com")
# 截图
bro.save_screenshot("./1.jpg")
# 根据find系列的函数定位到指定的标签
my_input = bro.find_element_by_id("kw")
# 向标签中录入指定的标签

my_input = bro.send_keys("美女")
# 知道百度一下的按钮
my_button = bro.find_element_by_id("su")
my_button.click()

# 获取浏览器当前的页面源码
page_text = bro.page_source
bro.save_screenshot("./2.png")  # 截图

print(page_text)
bro.quit()

from selenium import webdriver
import time
# 伪装一个谷歌浏览器(实例化一个谷歌浏览器的对象)
bro = webdriver.Chrome(executable_path=r"D:chromechromedriver.exe")

# 发送的请求
bro.get(url="https://www.baidu.com")
time.sleep(3)
# 根据find系列的函数定位到指定的标签(这个是输入框的标签)
my_input = bro.find_element_by_id("kw")

# 向标签中录入指定的数据
my_input.send_keys("美女")
time.sleep(3)
# 获取到点击按钮(百度一下)
my_button = bro.find_element_by_id("su")
# 点击搜索
my_button.click()
time.sleep(3)

# 获取到当前浏览器显示的页面的页面源码
page_text = bro.page_source
print(page_text)
# 退出
bro.quit()

qq空间登录的代码:

from lxml import etree
bro = webdriver.Chrome(executable_path=r"D:chromechromedriver.exe")
url = "https://qzone.qq.com/"

# 请求的发送
bro.get(url=url)
time.sleep(1)
# 定位到指定的iframe
bro.switch_to.frame("login_frame")
# 找到账号密码登录的标签
bro.find_element_by_id("switcher_plogin").click()
time.sleep(1)

# 找到登录的按钮,并点击登录

# 找到用户名的输入框并输入账号
username = bro.find_element_by_id("u")
username.send_keys("937371049")

# 找到密码并输入
password = bro.find_element_by_id("p")
password.send_keys("13633233754")

# 找到登录按钮点击登录
bro.find_element_by_id("login_button").click()
time.sleep(1)

# 找到js代码,滚轮 向下滚动
js = "window.scrollTo(0, document.body.scrollHeight)"

# 滚轮开始滚动
bro.execute_script(js)
time.sleep(2)
bro.execute_script(js)
time.sleep(2)
bro.execute_script(js)
time.sleep(2)
bro.execute_script(js)
time.sleep(2)
page_text = bro.page_source
time.sleep(3)

# 解析:
# 把 获取到的数据转化成html的格式
tree = etree.HTML(page_text)

div_list = tree.xpath('//div[@class="f-info qz_info_cut"] | //div[@class="f-info"]')
for div in div_list:
    text = div.xpath('.//text()')
    text = "".join(text)
    print(text)
bro.quit()

4,谷歌无头浏览器

由于phantomJS最近已经停止了更新和维护,所以大家使用谷歌无头浏览器

from selenium.webdriver.chrome.options import Options
chrome_options = Options()
chrome_options.add_argument("--headless")
chrome_options.add_argument("--disable-gpu")

# 谷歌无头浏览器

bro = webdriver.Chrome(executable_path=r"D:chromechromedriver.exe", chrome_options=chrome_options)

# 请求的发送
bro.get(url="https://www.baidu.com")

# 根据find系列的函数定位到指定的标签
my_input = bro.find_element_by_id("kw")

# 向标签中录入指定的元素
my_input.send_keys("美女")

my_button = bro.find_element_by_id("su")
# 点击百度
my_button.click()

# 获取当前浏览器显示的页面的页面源码
page_text = bro.page_source
print(page_text)
bro.quit()

5,UA池和代理池

咱们先去官网把scrapy框架的图拿出来see,see

下载中间件(Downloader Middlewares)位于引擎和下载器之间的一层组件
作用:
1. 引擎将请求传递给下载器过程中,下载中间件可以对请求进行一系列处理,比如设置请求的User-Agent,设置代理等
2. 在下载器完成将Response传递给引擎中,下载中间件可以对响应进行一系列处理,比如进行gzip解压等
我们主要使用下载中间件处理请求,一般会对请求,设置随机的User-Agent,设置随机的代理,目的在于防止爬取网站的反爬虫策略.

UA池:User-Agent池

应用:尽可能多的将scrapy工程中的请求伪装成不同类型额度浏览器身份
操作流程:
1. 在下载中间中拦截请求
2. 在拦截到的请求的请求头信息中的UA进行篡改伪装
3. 在配置文找中开启下载中间件
代码展示:

from scrapy import signals
import random


class CrawlproSpiderMiddleware(object):
    # Not all methods need to be defined. If a method is not defined,
    # scrapy acts as if the spider middleware does not modify the
    # passed objects.

    @classmethod
    def from_crawler(cls, crawler):
        # This method is used by Scrapy to create your spiders.
        s = cls()
        crawler.signals.connect(s.spider_opened, signal=signals.spider_opened)
        return s

    def process_spider_input(self, response, spider):
        # Called for each response that goes through the spider
        # middleware and into the spider.

        # Should return None or raise an exception.
        return None

    def process_spider_output(self, response, result, spider):
        # Called with the results returned from the Spider, after
        # it has processed the response.

        # Must return an iterable of Request, dict or Item objects.
        for i in result:
            yield i

    def process_spider_exception(self, response, exception, spider):
        # Called when a spider or process_spider_input() method
        # (from other spider middleware) raises an exception.

        # Should return either None or an iterable of Response, dict
        # or Item objects.
        pass

    def process_start_requests(self, start_requests, spider):
        # Called with the start requests of the spider, and works
        # similarly to the process_spider_output() method, except
        # that it doesn’t have a response associated.

        # Must return only requests (not items).
        for r in start_requests:
            yield r

    def spider_opened(self, spider):
        spider.logger.info('Spider opened: %s' % spider.name)


class CrawlproDownloaderMiddleware(object):
    # Not all methods need to be defined. If a method is not defined,
    # scrapy acts as if the downloader middleware does not modify the
    # passed objects.

    proxy_http = [
        "http://113.128.10.121", "http://49.86.181.235", "http://121.225.52.143", "http://180.118.134.29",
        "http://111.177.186.27", "http://175.155.77.189", "http://110.52.235.120", "http://113.128.24.189",
    ]
    proxy_https = [
        "https://93.190.143.59", "https://106.104.168.15", "https://167.249.181.237", "https://124.250.70.76",
        "https://119.101.115.2", "https://58.55.133.48", "https://49.86.177.193", "https://58.55.132.231",
        "https://58.55.133.77", "https://119.101.117.189", "https://27.54.248.42", "https://221.239.86.26",
    ]
    # 拦截请求:request参数就是拦截到的请求
    user_agent_list = [
        "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.1 "
        "(KHTML, like Gecko) Chrome/22.0.1207.1 Safari/537.1",
        "Mozilla/5.0 (X11; CrOS i686 2268.111.0) AppleWebKit/536.11 "
        "(KHTML, like Gecko) Chrome/20.0.1132.57 Safari/536.11",
        "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/536.6 "
        "(KHTML, like Gecko) Chrome/20.0.1092.0 Safari/536.6",
        "Mozilla/5.0 (Windows NT 6.2) AppleWebKit/536.6 "
        "(KHTML, like Gecko) Chrome/20.0.1090.0 Safari/536.6",
        "Mozilla/5.0 (Windows NT 6.2; WOW64) AppleWebKit/537.1 "
        "(KHTML, like Gecko) Chrome/19.77.34.5 Safari/537.1",
        "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/536.5 "
        "(KHTML, like Gecko) Chrome/19.0.1084.9 Safari/536.5",
        "Mozilla/5.0 (Windows NT 6.0) AppleWebKit/536.5 "
        "(KHTML, like Gecko) Chrome/19.0.1084.36 Safari/536.5",
        "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/536.3 "
        "(KHTML, like Gecko) Chrome/19.0.1063.0 Safari/536.3",
        "Mozilla/5.0 (Windows NT 5.1) AppleWebKit/536.3 "
        "(KHTML, like Gecko) Chrome/19.0.1063.0 Safari/536.3",
        "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_8_0) AppleWebKit/536.3 "
        "(KHTML, like Gecko) Chrome/19.0.1063.0 Safari/536.3",
        "Mozilla/5.0 (Windows NT 6.2) AppleWebKit/536.3 "
        "(KHTML, like Gecko) Chrome/19.0.1062.0 Safari/536.3",
        "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/536.3 "
        "(KHTML, like Gecko) Chrome/19.0.1062.0 Safari/536.3",
        "Mozilla/5.0 (Windows NT 6.2) AppleWebKit/536.3 "
        "(KHTML, like Gecko) Chrome/19.0.1061.1 Safari/536.3",
        "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/536.3 "
        "(KHTML, like Gecko) Chrome/19.0.1061.1 Safari/536.3",
        "Mozilla/5.0 (Windows NT 6.1) AppleWebKit/536.3 "
        "(KHTML, like Gecko) Chrome/19.0.1061.1 Safari/536.3",
        "Mozilla/5.0 (Windows NT 6.2) AppleWebKit/536.3 "
        "(KHTML, like Gecko) Chrome/19.0.1061.0 Safari/536.3",
        "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/535.24 "
        "(KHTML, like Gecko) Chrome/19.0.1055.1 Safari/535.24",
        "Mozilla/5.0 (Windows NT 6.2; WOW64) AppleWebKit/535.24 "
        "(KHTML, like Gecko) Chrome/19.0.1055.1 Safari/535.24"
    ]

    @classmethod
    def from_crawler(cls, crawler):
        # This method is used by Scrapy to create your spiders.
        s = cls()
        crawler.signals.connect(s.spider_opened, signal=signals.spider_opened)
        return s

    def process_request(self, request, spider):
        # Called for each request that goes through the downloader
        # middleware.

        # Must either:
        # - return None: continue processing this request
        # - or return a Response object
        # - or return a Request object
        # - or raise IgnoreRequest: process_exception() methods of
        #   installed downloader middleware will be called
        print("中间件开始下载", request)
        if request.url.split(":")[0] == "http":
            request.meta["proxy"] = random.choice(self.proxy_http)
        else:
            request.meta["proxy"] = random.choice(self.proxy_https)

        request.header["User-Agent"] = random.choice(self.user_agent_list)

        print(request.meta["proxy"], request.heaser["User-Agent"])
        return None

    def process_response(self, request, response, spider):
        # Called with the response returned from the downloader.

        # Must either;
        # - return a Response object
        # - return a Request object
        # - or raise IgnoreRequest


        return response

    def process_exception(self, request, exception, spider):
        # Called when a download handler or a process_request()
        # (from other downloader middleware) raises an exception.

        # Must either:
        # - return None: continue processing this exception
        # - return a Response object: stops process_exception() chain
        # - return a Request object: stops process_exception() chain
        pass

    def spider_opened(self, spider):
        spider.logger.info('Spider opened: %s' % spider.name)

代理池

作用尽可能多的将scrapy工程中的请求的IP设置成不同的
操作流程:
1. 在下载中间件中拦截请求
2. 将拦截到的请求的IP修改成某一代理IP
3. 在配置文件中开启下载中间件

代码展示:上边代码里有,参考上边代码即可.

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原文地址：https://www.cnblogs.com/ljc-0923/p/10331782.html