selenium知识点

1. 导包

 from selenium import webdriver
 from selenium.webdriver.support.ui import WebDriverWait
 from selenium.webdriver.support import expected_conditions as ec
 from selenium.webdriver.common.by import By

2. 创建 webdriver

driver = webdriver.Chrome(executable_path=r'C:python35chromedriver.exe')

# executable_path：chromedriver.exe的存放路径

3. 操作

1. 常用操作

driver.page_source   # 响应页面,element标签
driver.title         # 请求页面的title
driver.current_url   # 请求的url
driver.close()       # 关闭浏览器窗口
driver.quit()        # 退出浏览器
driver.current_window_handle  # 获取当前窗口的句柄
driver.window_handles         # 获取所有窗口的句柄
driver.switch_to_window()   # 切换浏览器窗口
driver.execute_script()     # 执行js脚本(在打开新窗口时用)
driver.get_cookie()         # 获取cookie
driver.find_element_by_class_name()   # 根据class查找标签
driver.find_element_by_xpath()        # 根据xpath查找标签

4 例子 -- 爬去拉钩网招聘信息

过程： 用 selenium 访问首页，然后用lxml解析首页上的每一个职位，获取职位的链接地址，然后再用selenium 访问该地址，用lxml提取职位详情的信息。

• get_attribute('class')  # 获取标签的class属性值

• self.driver.execute_script('window.open("https://www.baidu.com/")')  # 打开一个新窗口 (请求详情页)  通过执行js脚本打开新的窗口

• self.driver.switch_to.window(self.driver.window_handles[1])   # 将driver切换到新窗口（详情页窗口）

• WebDriverWait(driver=self.driver, timeout=10). 
              until(ec.presence_of_element_located((By.XPATH, '//span[@class="name"]')))  # 显示等待（职位详情页，出现职位标题为条件），在等待过程中如果出现要寻找的标签，则结束等待，如果没有出现则一直等待，直到10s，抛出异常。注意：这里只能定位某个标签，不能取标签里面的值，如这里的span标签中的值。

• 注意：在切换到新窗口后，如果想继续在原始窗口执行操作，需要再重新切回原始窗口，如这里的由详情页窗口切换到列表页窗口。

import re
import time
import csv
from lxml import etree
from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.support import expected_conditions as ec
from selenium.webdriver.support.ui import WebDriverWait


class LaGouSpider:
    def __init__(self):
        self.driver = webdriver.Chrome(executable_path=r'C:python35chromedriver.exe')
        self.init_url = 'https://www.lagou.com/zhaopin/Python/'
        self.next_page = True
        self.position = None
        self.csv_header = ['职位名称', '职位要求', '薪水', '职位标签', '职位诱惑', '职位详情', '发布时间']
        self.is_writer_header = False

    def request_list_page(self, url=None):
        if url:
            self.driver.get(url)
        html = etree.HTML(self.driver.page_source)
        # 解析html 获取职位列表
        links = html.xpath('//a[@class="position_link"]/@href')
        for link in links:
            self.request_detail_page(link)
            time.sleep(1)
        # 下一页
        next_btn = self.driver.find_element_by_xpath('//div[@class="pager_container"]/a[last()]')
        if 'page_no pager_next_disabled' not in next_btn.get_attribute('class'):
            next_btn.click()
        else:
            self.next_page = False

    def request_detail_page(self, url):
        # 打开一个新窗口 (请求详情页)
        self.driver.execute_script('window.open("' + url + '")')
        # 将driver切换到新窗口（详情页窗口）
        self.driver.switch_to.window(self.driver.window_handles[1])
        # 显示等待（职位详情页，出现职位标题为条件）
        WebDriverWait(driver=self.driver, timeout=10). 
            until(ec.presence_of_element_located((By.XPATH, '//span[@class="name"]')))
        # 解析详情页
        self.parse_detail_page(self.driver.page_source)
        # 关闭新窗口
        self.driver.close()
        # 重新将窗口切回到列表页窗口
        self.driver.switch_to.window(self.driver.window_handles[0])

    def parse_detail_page(self, source):
        html = etree.HTML(source)
        position_name = html.xpath('//span[@class="name"]/text()')
        job_request = html.xpath('//dd[@class="job_request"]/p//text()')
        position_label = html.xpath('//ul[@class="position-label clearfix"]//text()')
        publish_time = html.xpath('//p[@class="publish_time"]//text()')
        job_advantage = html.xpath('//dd[@class="job-advantage"]/p/text()')
        job_detail = html.xpath('//div[@class="job-detail"]/p/text()')

        # 清洗数据
        position_name = position_name[0] if position_name else None
        job_request = [re.sub('
|/|\xa0', '', i).strip() for i in job_request] if job_request else None
        job_request = [i for i in job_request if i != '']
        # 提取salary
        salary = job_request[0] if len(job_request) > 2 else None
        # 提取职位需求
        job_request = ','.join(job_request[2:5])
        # 职位标签
        position_label = [re.sub('
|/|\xa0', '', i).strip() for i in position_label] if position_label else None
        position_label = ','.join([i for i in position_label if i != ''])
        # 职位诱惑
        job_advantage = job_advantage[0] if job_advantage else None
        # 发布时间
        print(publish_time)

        print(salary)
        publish_time = re.match(r'd+天w|d+:d+', publish_time[0]).group() if publish_time else  None
        # 职位详情
        job_detail = ','.join([a.strip() for a in job_detail] if job_detail else None)
        position = {
            '职位名称': position_name,
            '职位要求': job_request,
            '薪水': salary,
            '职位标签': position_label,
            '职位诱惑': job_advantage,
            '职位详情': job_detail,
            '发布时间': publish_time,
        }
        self.write_csv(position)

    def write_csv(self, position):
        with open('position.csv', 'a+', encoding='utf-8', newline='') as f:
            writer = csv.DictWriter(f, self.csv_header)
            if not self.is_writer_header:
                writer.writeheader()
                self.is_writer_header = True
            writer.writerow(position)

    def run(self):
        self.request_list_page(self.init_url)
        while self.next_page:
            self.request_list_page()

if __name__ == '__main__':
    lagou = LaGouSpider()
    lagou.run()

 5. Selenium 的 WebDriverWait

https://blog.csdn.net/duzilonglove/article/details/78455051