selenium 是一个用于Web自动化测试的工具。selenium在爬虫，主要是用来解决javascript渲染的问题 。也就是requests或者urlib库无法正常获取网页内容的时候，可以考虑使用selenium

安装

pip insatll selenium
由于如果需要使用selenium的话，需要为本机配置对应浏览器的驱动，下面以chomedriver为例，首先安装chromedriver，chrome版本可以在标签页输入chrome://version/看到。chromedriver下载地址,其版本与支持对应的chrome版本如下：
v2.41 v67-69
v2.40 v66-68
v2.39 v66-68
v2.38 v65-67
v2.37 v64-66
v2.36 v63-65
v2.35 v62-64
v2.34 v61-63
v2.33 v60-62
v2.32 v59-61
v2.31 v58-60
v2.30 v58-60
v2.29 v56-58
v2.28 v55-57
v2.27 v54-56
v2.26 v53-55
v2.25 v53-55
v2.24 v52-54
v2.23 v51-53
v2.22 v49-52
v2.21 v46-50
v2.20 v43-48
chromedriver解压后放到Python或者其他配置了环境变量的目录下。

基本使用

from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.common.keys import Keys
from selenium.webdriver.support import expected_conditions as EC
from selenium.webdriver.support.wait import WebDriverWait

browser = webdriver.Chrome()
try:
    browser.get('https://www.baidu.com')
    input = browser.find_element_by_id('kw')
    input.send_keys('Python')
    input.send_keys(Keys.ENTER)
    wait = WebDriverWait(browser, 10)
    wait.until(EC.presence_of_element_located((By.ID, 'content_left')))
    print(browser.current_url)
    print(browser.get_cookies())
    print(browser.page_source)
finally:
    browser.close()

声明浏览器对象

from selenium import webdriver

browser = webdriver.Chrome()
browser = webdriver.Firefox()
browser = webdriver.Edge()
browser = webdriver.PhantomJS()
browser = webdriver.Safari()

访问页面

from selenium import webdriver

browser = webdriver.Chrome()
browser.get('https://www.taobao.com')
print(browser.page_source)
browser.close()

查找元素

现在我们已经将网页打开，那我们该如何进行交互呢？要想交互，首先就需要找到需要交互的元素

• find_element_by_name
• find_element_by_xpath
• find_element_by_link_text
• find_element_by_partial_link_text
• find_element_by_tag_name
• find_element_by_class_name
• find_element_by_css_selector

单个元素

from selenium import webdriver

browser = webdriver.Chrome()
browser.get('https://www.taobao.com')
input_first = browser.find_element_by_id('q')
input_second = browser.find_element_by_css_selector('#q')
input_third = browser.find_element_by_xpath('//*[@id="q"]')
print(input_first, input_second, input_third)
browser.close()

from selenium import webdriver
from selenium.webdriver.common.by import By

browser = webdriver.Chrome()
browser.get('https://www.taobao.com')
input_first = browser.find_element(By.ID, 'q')
print(input_first)
browser.close()

多个元素

from selenium import webdriver

browser = webdriver.Chrome()
browser.get('https://www.taobao.com')
lis = browser.find_elements_by_css_selector('.service-bd li')
print(lis)
browser.close()

from selenium import webdriver
from selenium.webdriver.common.by import By

browser = webdriver.Chrome()
browser.get('https://www.taobao.com')
lis = browser.find_elements(By.CSS_SELECTOR, '.service-bd li')
print(lis)
browser.close()

元素交互操作

from selenium import webdriver
import time

browser = webdriver.Chrome()
browser.get('https://www.taobao.com')
input = browser.find_element_by_id('q')
input.send_keys('iPhone')
time.sleep(1)
input.clear()
input.send_keys('iPad')
button = browser.find_element_by_class_name('btn-search')
button.click()

更多操作: http://selenium-python.readthedocs.io/api.html#module-selenium.webdriver.remote.webelement

交互动作

将动作附加到动作链中串行执行

from selenium import webdriver
from selenium.webdriver import ActionChains

browser = webdriver.Chrome()
url = 'http://www.runoob.com/try/try.php?filename=jqueryui-api-droppable'
browser.get(url)
browser.switch_to.frame('iframeResult')
source = browser.find_element_by_css_selector('#draggable')
target = browser.find_element_by_css_selector('#droppable')
actions = ActionChains(browser)
actions.drag_and_drop(source, target)
actions.perform()

更多操作: http://selenium-python.readthedocs.io/api.html#module-selenium.webdriver.common.action_chains

执行JavaScript

from selenium import webdriver

browser = webdriver.Chrome()
browser.get('https://www.zhihu.com/explore')
browser.execute_script('window.scrollTo(0, document.body.scrollHeight)')
browser.execute_script('alert("To Bottom")')

获取元素信息

获取属性

from selenium import webdriver
from selenium.webdriver import ActionChains

browser = webdriver.Chrome()
url = 'https://www.zhihu.com/explore'
browser.get(url)
logo = browser.find_element_by_id('zh-top-link-logo')
print(logo)
print(logo.get_attribute('class'))

获取文本值

from selenium import webdriver

browser = webdriver.Chrome()
url = 'https://www.zhihu.com/explore'
browser.get(url)
input = browser.find_element_by_class_name('zu-top-add-question')
print(input.text)

Frame

import time
from selenium import webdriver
from selenium.common.exceptions import NoSuchElementException

browser = webdriver.Chrome()
url = 'http://www.runoob.com/try/try.php?filename=jqueryui-api-droppable'
browser.get(url)
browser.switch_to.frame('iframeResult')
source = browser.find_element_by_css_selector('#draggable')
print(source)
try:
    logo = browser.find_element_by_class_name('logo')
except NoSuchElementException:
    print('NO LOGO')
browser.switch_to.parent_frame()
logo = browser.find_element_by_class_name('logo')
print(logo)
print(logo.text)

等待

隐式等待

当使用了隐式等待执行测试的时候，如果 WebDriver没有在 DOM中找到元素，将继续等待，超出设定时间后则抛出找不到元素的异常, 换句话说，当查找元素或元素并没有立即出现的时候，隐式等待将等待一段时间再查找 DOM，默认的时间是0

from selenium import webdriver

browser = webdriver.Chrome()
browser.implicitly_wait(10)
browser.get('https://www.zhihu.com/explore')
input = browser.find_element_by_class_name('zu-top-add-question')
print(input)

显式等待

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

browser = webdriver.Chrome()
browser.get('https://www.taobao.com/')
wait = WebDriverWait(browser, 10)
input = wait.until(EC.presence_of_element_located((By.ID, 'q')))
button = wait.until(EC.element_to_be_clickable((By.CSS_SELECTOR, '.btn-search')))
print(input, button)

• title_is 标题是某内容
• title_contains 标题包含某内容
• presence_of_element_located 元素加载出，传入定位元组，如(By.ID, 'p')
• visibility_of_element_located 元素可见，传入定位元组
• visibility_of 可见，传入元素对象
• presence_of_all_elements_located 所有元素加载出
• text_to_be_present_in_element 某个元素文本包含某文字
• text_to_be_present_in_element_value 某个元素值包含某文字
• frame_to_be_available_and_switch_to_it frame加载并切换
• invisibility_of_element_located 元素不可见
• element_to_be_clickable 元素可点击
• staleness_of 判断一个元素是否仍在DOM，可判断页面是否已经刷新
• element_to_be_selected 元素可选择，传元素对象
• element_located_to_be_selected 元素可选择，传入定位元组
• element_selection_state_to_be 传入元素对象以及状态，相等返回True，否则返回False
• element_located_selection_state_to_be 传入定位元组以及状态，相等返回True，否则返回False
• alert_is_present 是否出现Alert
  详细内容：http://selenium-python.readthedocs.io/api.html#module-selenium.webdriver.support.expected_conditions

Cookies

from selenium import webdriver

browser = webdriver.Chrome()
browser.get('https://www.zhihu.com/explore')
print(browser.get_cookies())
browser.add_cookie({'name': 'name', 'domain': 'www.zhihu.com', 'value': 'germey'})
print(browser.get_cookies())
browser.delete_all_cookies()
print(browser.get_cookies())