上一篇文章《selenium webdriver 是怎么运行的》用了一个简单的例子——搭出租车，形象地讲解selenium webdriver 是如何运行的，而这一篇文章可以理解为深入了解selenium是如何和浏览器驱动进行交互，也可以认为是乙醇老师写的《selenium是如何启动浏览器的》 文章的2.0版本 。
环境准备：
python 3.0以上
selenium 3.0以上
浏览器 Chrome
浏览器驱动 ChromeDriver
接口测试工具
小编的环境：
python 3.6.4
selenium 3.13
浏览器 ：Chrome 68
浏览器驱动： ChromeDriver 2.38
接口测试工具：python requests
首先，我们运行下述代码块
#encoding:utf8
from selenium import webdriver
import logging
logging.basicConfig(level=logging.DEBUG)
dr = webdriver.Chrome()
dr.implicitly_wait(10)
#打开深圳-逸遥 博客园首页
dr.get('https://www.cnblogs.com/snailrunning')
#定位深圳-逸遥 第一篇博文标题
el = dr.find_element_by_css_selector('.postTitle a')
#点击第一篇博文标题
el.click()
运行结果：
DEBUG:selenium.webdriver.remote.remote_connection:
POST :4102/session
{"capabilities": {"firstMatch": [{}], "alwaysMatch": {"browserName":
"chrome", "platformName": "any", "goog:chromeOptions": {"extensions": [], "args": []}}},
"desiredCapabilities": {"browserName": "chrome", "version": "", "platform": "ANY", "goog:chromeOptions": {"extensions": [], "args": []}}}
DEBUG:selenium.webdriver.remote.remote_connection:
b'{"sessionId":"7cbbff953318267ef0089dc66f127051",
"status":0,
"value":{"acceptInsecureCerts":false,"acceptSslCerts":false,"applicationCacheEnabled":false,"browserConnectionEnabled":false,"browserName":"chrome","chrome":{"chromedriverVersion":"2.38.552522 (437e6fbedfa8762dec75e2c5b3ddb86763dc9dcb)","userDataDir":"C:\\\\Users\\\\lenovo\\\\AppData\\\\Local\\\\Temp\\\\scoped_dir13812_4179"},"cssSelectorsEnabled":true,"databaseEnabled":false,"handlesAlerts":true,"hasTouchScreen":false,"javascriptEnabled":true,"locationContextEnabled":true,"mobileEmulationEnabled":false,"nativeEvents":true,"networkConnectionEnabled":false,"pageLoadStrategy":"normal","platform":"Windows NT","rotatable":false,"setWindowRect":true,"takesHeapSnapshot":true,"takesScreenshot":true,"unexpectedAlertBehaviour":"","version":"68.0.3440.106","webStorageEnabled":true}}'
DEBUG:selenium.webdriver.remote.remote_connection:Finished Request
DEBUG:selenium.webdriver.remote.remote_connection:
POST
:4102/session/7cbbff953318267ef0089dc66f127051/timeouts/implicit_wait
{"ms": 10000.0, "sessionId": "7cbbff953318267ef0089dc66f127051"}
DEBUG:selenium.webdriver.remote.remote_connection:
b'{"sessionId":"7cbbff953318267ef0089dc66f127051","status":0,"value":null}'
DEBUG:selenium.webdriver.remote.remote_connection:Finished Request
DEBUG:selenium.webdriver.remote.remote_connection:
POST :4102/session/7cbbff953318267ef0089dc66f127051/url
{"url": "https://www.cnblogs.com/snailrunning", "sessionId": "7cbbff953318267ef0089dc66f127051"}
DEBUG:selenium.webdriver.remote.remote_connection:
b'{"sessionId":"7cbbff953318267ef0089dc66f127051","status":0,"value":null}'
DEBUG:selenium.webdriver.remote.remote_connection:Finished Request
DEBUG:selenium.webdriver.remote.remote_connection:
POST
:4102/session/7cbbff953318267ef0089dc66f127051/element
{"using": "css selector", "value": ".postTitle a", "sessionId": "7cbbff953318267ef0089dc66f127051"}
DEBUG:selenium.webdriver.remote.remote_connection:
b'{"sessionId":"7cbbff953318267ef0089dc66f127051","status":0,"value":{"ELEMENT":"0.3612689441010788-1"}}'
DEBUG:selenium.webdriver.remote.remote_connection:Finished Request
DEBUG:selenium.webdriver.remote.remote_connection:
POST :4102/session/7cbbff953318267ef0089dc66f127051/element/0.3612689441010788-1/click
{"id": "0.3612689441010788-1", "sessionId": "7cbbff953318267ef0089dc66f127051"}
DEBUG:selenium.webdriver.remote.remote_connection:
b'{"sessionId":"7cbbff953318267ef0089dc66f127051","status":0,"value":null}'
DEBUG:selenium.webdriver.remote.remote_connection:Finished Request
从上述代码运行结果，我们可以得出以下结论
对于每个Selenium命令，都会创建一个HTTP请求并将其发送到浏览器驱动程序
每一个命令的执行结果都会返回给自动化代码
ChromeDirver创建session时打开了浏览器
Selenium代码和浏览器驱动的交互都根据ChromeDriver创建的sessionId
文章到这里，很多测试的同学看了会头晕，没关系，我们现在先根据上述返回的结果来拆解一下请求的接口和返回，以及我们通过接口工具来模拟Selenium
自动化代码来操纵浏览器
1、启动浏览器接口
请求方式：post
请求url : :4102/session
请求body: {"capabilities": {"firstMatch": [{}], "alwaysMatch": {"browserName":
"chrome", "platformName": "any", "goog:chromeOptions": {"extensions": [], "args": []}}},
"desiredCapabilities": {"browserName": "chrome", "version": "", "platform": "ANY", "goog:chromeOptions": {"extensions": [], "args": []}}}
返回body : b'{"sessionId":"7cbbff953318267ef0089dc66f127051",
"status":0,
"value":{"acceptInsecureCerts":false,"acceptSslCerts":false,"applicationCacheEnabled":false,"browserConnectionEnabled":false,"browserName":"chrome","chrome":{"chromedriverVersion":"2.38.552522 (437e6fbedfa8762dec75e2c5b3ddb86763dc9dcb)","userDataDir":"C:\\\\Users\\\\lenovo\\\\AppData\\\\Local\\\\Temp\\\\scoped_dir13812_4179"},"cssSelectorsEnabled":true,"databaseEnabled":false,"handlesAlerts":true,"hasTouchScreen":false,"javascriptEnabled":true,"locationContextEnabled":true,"mobileEmulationEnabled":false,"nativeEvents":true,"networkConnectionEnabled":false,"pageLoadStrategy":"normal","platform":"Windows NT","rotatable":false,"setWindowRect":true,"takesHeapSnapshot":true,"takesScreenshot":true,"unexpectedAlertBehaviour":"","version":"68.0.3440.106","webStorageEnabled":true}}'
1.1 开启ChomeDriver
