Is Chrome installation needed or only chromedriver when using Selenium?

问题

I've tried to search, but haven't found a definitive answer. On Windows Server 2016 WITHOUT Chrome Browser actually installed. I downloaded the correct "chromedriver.exe" and placed it in "D:\Apps\chromedriver.exe". I have added to my environment PATH the full path as "D:\Apps\chromedriver.exe".

When I attempt to start my Windows Service that utilizes the latest Selenium, I get the following error:

Exception occurred: Failed initializing web driver: Message: unknown error: cannot find Chrome binary
  (Driver info: chromedriver=2.40.565498 (ea082db3280dd6843ebfb08a625e3eb905c4f5ab),platform=Windows NT 10.0.14393 x86_64)

Question: Do I have to actually install the full-blown browser in addition to the chromedriver, or is this simply just not finding the chromedriver.exe in my Python code (included below for full disclosure):

def __init__(self, username, password, environment='cert'):
    self.username = username
    self.password = password
    self.environment = environment

    # Instantiate a chrome options object so you can set the size and headless preference
    self.chrome_options = Options()

    # Toggle Headless or not
    if HEADLESS_TOGGLE == 1:
        self.chrome_options.add_argument("--headless")

    self.chrome_options.add_argument("--disable-gpu")  # Disables "Lost UI Shared Context GPU Error on Windows"
    self.chrome_options.add_argument('--disable-extensions')  # Disables Extensions
    self.chrome_options.add_argument("--disable-software-rasterizer")  # Disables "Lost UI Shared Context GPU Error on Windows"
    self.chrome_options.add_argument("--window-size=1024x768")
    self.chrome_options.add_argument("--log-level=3")  # Errors Only
    self.chrome_options.add_argument("--incognito")  # Keeps history and logs clear
    self.chrome_options.add_argument("--no-sandbox")
    self.chrome_options.add_argument("--mute_audio")  # No loud surprises!
    self.chrome_options.add_argument("--no-gpu")  # Disables gpu-based errors (headless)

    self.driver = webdriver.Chrome(chrome_options=self.chrome_options)

回答1:

This error message...

Exception occurred: Failed initializing web driver: Message: unknown error: cannot find Chrome binary
  (Driver info: chromedriver=2.40.565498 (ea082db3280dd6843ebfb08a625e3eb905c4f5ab),platform=Windows NT 10.0.14393 x86_64)

...implies that the ChromeDriver was unable to find the Chrome binary while trying to initiate a new new Browsing Context i.e. Chrome Browser session.

As per the documentation with in the wiki page of ChromeDriver:

ChromeDriver is a standalone server which earlier implemented the WebDriver's wire protocol but slowly and gradually shifting it's implementation as per WebDriver standard.
The ChromeDriver consists of three separate pieces.
- There is the browser itself i.e. chrome
- The language bindings provided by the Selenium project i.e. the driver
- An executable downloaded from the Chromium project which acts as a bridge between chrome and the driver which is called chromedriver and we refer to it as the server.
In generic scenarios the server expects you to have Chrome installed in the default location for each system:
- Linux: /usr/bin/google-chrome ¹
- Mac: /Applications/Google\ Chrome.app/Contents/MacOS/Google\ Chrome
- Windows XP: %HOMEPATH%\Local Settings\Application Data\Google\Chrome\Application\chrome.exe
- Windows Vista and newer: C:\Users\%USERNAME%\AppData\Local\Google\Chrome\Application\chrome.exe

Note: ¹: For Linux systems, the ChromeDriver expects /usr/bin/google-chrome to be a symlink to the actual Chrome binary.

You can find a detailed discussion on overriding the default Chrome binary location in WebDriverException: unknown error: cannot find Chrome binary error with Selenium in Python for older versions of Google Chrome

Solution

So ideally to execute your tests using ChromeDriver / Chrome combo you need to:

Install the full-blown google-chrome browser.
Download the compatible version of chromedriver.exe
Quick installation of ChromeDriver:
- Mac users with Homebrew: brew tap homebrew/cask && brew cask install chromedriver
- Debian based Linux distros: sudo apt-get install chromium-chromedriver
- Windows users with Chocolatey installed: choco install chromedriver
You can find a couple of relevant discussions in:
- How to work with a specific version of ChromeDriver while Chrome Browser gets updated automatically through Python selenium
- Selenium for ChromeDriver and Chrome Browser and the log message “Only local connections are allowed”
- WebDriverException: Message: Service /usr/lib/chromium-browser/chromedriver unexpectedly exited on Raspberry-Pi with ChromeDriver and Selenium