隨筆記錄方便自己和同路人查閱。
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Remote應用
要解釋清楚Remote的作用並不太容易，不過我們可以通過分析selenium代碼的方式來理解它的作用。我們知道WebDriver支持多瀏覽器下的執行，這是因為WebDriver針對每一種瀏覽器驅動都重寫WebDriver方法。所以，在腳本運行之前需要先確定瀏覽器驅動，具體如下：
driver = webdriver.Firefox() driver = webdriver.Chrome() driver = webdriver.Ie()
下面就對這些驅動進行簡單分析。
WebDriver驅動分析
在selenium包的WebDriver目錄下可以看到如下圖所示的目錄結構。
查看其中任何一個驅動的目錄發現都有一個webdriver.py文件，除了我們熟悉的Firefox、Chrome、IE等驅動外，其中還包括非常重要的remote。從這個角度看，也可以把它看作是一種驅動類型，而這種驅動類型比較特殊，它不是支持某一款特定的瀏覽器或平台而是一種配置模式，我們在這種配置模式下制定任意的平台或瀏覽器，這種模式的執行都需要Selenium Server的支持。
打開Selenium包下的webdriver/firefox目錄，先看Firefox中webdriver.py文件的實現。
from selenium.webdriver.common.desired_capabilities import DesiredCapabilities from selenium.webdriver.remote.webdriver import WebDriver as RemoteWebDriver from .extension_connection import ExtensionConnection from .firefox_binary import FirefoxBinary from .firefox_profile import FirefoxProfile from .options import Options from .remote_connection import FirefoxRemoteConnection from .service import Service from .webelement import FirefoxWebElement class WebDriver(RemoteWebDriver): # There is no native event support on Mac NATIVE_EVENTS_ALLOWED = sys.platform != "darwin" CONTEXT_CHROME = "chrome" CONTEXT_CONTENT = "content" _web_element_cls = FirefoxWebElement def __init__(self, firefox_profile=None, firefox_binary=None, timeout=30, capabilities=None, proxy=None, executable_path="geckodriver", options=None, service_log_path="geckodriver.log", firefox_options=None, service_args=None, desired_capabilities=None, log_path=None, keep_alive=True):
主機查看WebDriver類的__init__()初始化方法，因為Selenium自帶Firefox瀏覽器驅動，所以，這個驅動的重要配置在於firefox_profile和firefox_binary兩個參數。而這兩個參數分別調用當前目錄下的firefox_binary.py和firefox_profile.py文件，感興趣的讀者可以進一步研究這兩個文件的實現。
我們在腳本中調用Firefox瀏覽器驅動時的路徑為：selenium.webdriver.Firefox()，那么，它是如何指向../selenium/webdriver/firefox/webdriver.py文件中WebDriver類的內？秘密在於../selenium/webdriver/目錄下的__init__.py文件。查看__init__.py文件
from .firefox.webdriver import WebDriver as Firefox # noqa from .firefox.firefox_profile import FirefoxProfile # noqa from .firefox.options import Options as FirefoxOptions # noqa from .chrome.webdriver import WebDriver as Chrome # noqa from .chrome.options import Options as ChromeOptions # noqa from .ie.webdriver import WebDriver as Ie # noqa from .ie.options import Options as IeOptions # noqa from .edge.webdriver import WebDriver as Edge # noqa from .opera.webdriver import WebDriver as Opera # noqa from .safari.webdriver import WebDriver as Safari # noqa from .blackberry.webdriver import WebDriver as BlackBerry # noqa from .phantomjs.webdriver import WebDriver as PhantomJS # noqa from .android.webdriver import WebDriver as Android # noqa from .webkitgtk.webdriver import WebDriver as WebKitGTK # noqa from .webkitgtk.options import Options as WebKitGTKOptions # noqa from .remote.webdriver import WebDriver as Remote # noqa from .common.desired_capabilities import DesiredCapabilities # noqa from .common.action_chains import ActionChains # noqa from .common.touch_actions import TouchActions # noqa from .common.proxy import Proxy # noqa __version__ = '3.14.1'
通過查看該文件就明白了它的原理，它其實對不同驅動的路徑做了簡化，並且將不同目錄下的WebDriver類重命名為相應的瀏覽器（Firefox、Chrome、IE等），所以，在調用不同瀏覽器的驅動時就簡化了層級。
再打開selenium包下的webdriver/chrome目錄，查看Chrome中webdriver.py文件的實現。
import warnings from selenium.webdriver.remote.webdriver import WebDriver as RemoteWebDriver from .remote_connection import ChromeRemoteConnection from .service import Service from .options import Options class WebDriver(RemoteWebDriver): """ Controls the ChromeDriver and allows you to drive the browser. You will need to download the ChromeDriver executable from http://chromedriver.storage.googleapis.com/index.html """ def __init__(self, executable_path="chromedriver", port=0, options=None, service_args=None, desired_capabilities=None, service_log_path=None, chrome_options=None, keep_alive=True):
同樣查看WebDriver類的__init__()初始化方法，因為Selenium模塊不自帶chromedriver.exe驅動，隨意executable_path參數會指定chromedriver驅動。
通過查看兩個文件注意到一個細節，是Firefox和Chrome的WebDriver類都繼承RemoteWebDriver類，也就是remote的WebDriver類，那么我們很好奇這個WebDriver類實現了什么功能呢？
打開selenium包下webdriver/remote目錄下的webdriver.py文件。
class WebDriver(object): _web_element_cls = WebElement def __init__(self, command_executor='http://127.0.0.1:4444/wd/hub', desired_capabilities=None, browser_profile=None, proxy=None, keep_alive=False, file_detector=None, options=None): """ Create a new driver that will issue commands using the wire protocol. :Args: - command_executor - Either a string representing URL of the remote server or a custom remote_connection.RemoteConnection object. Defaults to 'http://127.0.0.1:4444/wd/hub'. - desired_capabilities - A dictionary of capabilities to request when starting the browser session. Required parameter. - browser_profile - A selenium.webdriver.firefox.firefox_profile.FirefoxProfile object. Only used if Firefox is requested. Optional. - proxy - A selenium.webdriver.common.proxy.Proxy object. The browser session will be started with given proxy settings, if possible. Optional. - keep_alive - Whether to configure remote_connection.RemoteConnection to use HTTP keep-alive. Defaults to False. - file_detector - Pass custom file detector object during instantiation. If None, then default LocalFileDetector() will be used. - options - instance of a driver options.Options class """ capabilities = {} if options is not None: capabilities = options.to_capabilities() if desired_capabilities is not None: if not isinstance(desired_capabilities, dict): raise WebDriverException("Desired Capabilities must be a dictionary") else: capabilities.update(desired_capabilities) if proxy is not None: warnings.warn("Please use FirefoxOptions to set proxy", DeprecationWarning, stacklevel=2) proxy.add_to_capabilities(capabilities) self.command_executor = command_executor if type(self.command_executor) is bytes or isinstance(self.command_executor, str): self.command_executor = RemoteConnection(command_executor, keep_alive=keep_alive) self._is_remote = True self.session_id = None self.capabilities = {} self.error_handler = ErrorHandler() self.start_client() if browser_profile is not None: warnings.warn("Please use FirefoxOptions to set browser profile", DeprecationWarning, stacklevel=2) self.start_session(capabilities, browser_profile) self._switch_to = SwitchTo(self) self._mobile = Mobile(self) self.file_detector = file_detector or LocalFileDetector()
WebDriver類的__init__()初始化方法提供了一個重要信息，即command_executor參數，它默認指向本機（127.0.0.1）的444端口號，通過修改這個參數可以使其指向任意的某平台主機。
除此之外，我們還需要對瀏覽器進行配置。瀏覽器的配置由desired_capabilities參數決定，這個參數的秘密在selenium包的webdriver/common目錄下的desired_capabilities.py文件中。
class DesiredCapabilities(object): FIREFOX = { "browserName": "firefox", "marionette": True, "acceptInsecureCerts": True, } INTERNETEXPLORER = { "browserName": "internet explorer", "version": "", "platform": "WINDOWS", } EDGE = { "browserName": "MicrosoftEdge", "version": "", "platform": "WINDOWS" } CHROME = { "browserName": "chrome", "version": "", "platform": "ANY", } OPERA = { "browserName": "opera", "version": "", "platform": "ANY", } SAFARI = { "browserName": "safari", "version": "", "platform": "MAC", } HTMLUNIT = { "browserName": "htmlunit", "version": "", "platform": "ANY", } HTMLUNITWITHJS = { "browserName": "htmlunit", "version": "firefox", "platform": "ANY", "javascriptEnabled": True, } IPHONE = { "browserName": "iPhone", "version": "", "platform": "MAC", } IPAD = { "browserName": "iPad", "version": "", "platform": "MAC", } ANDROID = { "browserName": "android", "version": "", "platform": "ANDROID", } PHANTOMJS = { "browserName": "phantomjs", "version": "", "platform": "ANY", "javascriptEnabled": True, } WEBKITGTK = { "browserName": "MiniBrowser", "version": "", "platform": "ANY", }
‘browserName’:’chrome’ 瀏覽器（Chrome、Firefox）
‘version’:’’ 瀏覽器版本。
‘platfrom’:’ANY’ 測試平台（ANY表示默認平台）
‘javascriptEnabled’:’True’ JavaScript啟動狀態。
‘marionette’:False marionette是Python客戶端允許你遠程控制基於gecko的瀏覽器或設備運行一個marionette服務器，包括桌面Firefox和Firefox OS。該參數為Firefox特有。
DesiredCapabilities平台及瀏覽器的參數如下
FIREFOX = { "browserName": "firefox", "version": "", "platform": "ANY", "javascriptEnabled":"True", "marionette":"False" } INTERNETEXPLORER = { "browserName": "internet explorer", "version": "", "platform": "WINDOWS", "javascriptEnabled":True, } EDGE = { "browserName": "MicrosoftEdge", "version": "", "platform": "WINDOWS", } CHROME = { "browserName": "chrome", "version": "", "platform": "ANY", "javascriptEnabled":True, } OPERA = { "browserName": "opera", "version": "", "platform": "ANY", "javascriptEnabled":True, } SAFARI = { "browserName": "safari", "version": "", "platform": "ANY", "javascriptEnabled":True, } HTMLUNITWITHJS = { "browserName": "htmlunit", "version": "firefox", "platform": "ANY", "javascriptEnabled":True, } IPHONE = { "browserName": "iPhone", "version": "", "platform": "MAC", "javascriptEnabled":True, } IPAD = { "browserName": "iPad", "version": "", "platform": "MAC", "javascriptEnabled":True, } ANDROID = { "browserName": "android", "version": "", "platform": "ANDROID", "javascriptEnabled":True, } PHANTOMJS = { "browserName": "phantomjs", "version": "", "platform": "ANY", "javascriptEnabled":True, }