Selenium源码学习

1 existing_ld_lib_path = os.environ.get('LD_LIBRARY_PATH', '')

该语句是将名为LD_LIBRARY_PATH的环境变量赋予existing_ld_lib_path

2 shutil.copy(os.path.join(os.path.dirname(__file__), path,self.NO_FOCUS_LIBRARY_NAME), library_path)

将 library_path中的文件复制到os.path.dirname(__file__), path,self.NO_FOCUS_LIBRARY_NAME)中的文件去。

3 key = OpenKey(HKEY_LOCAL_MACHINE, path)

打开注册表中特定KEY 该方法用于注册表寻找程序

4 self.process = Popen( command, stdout=self._log_file, stderr=STDOUT, env=self._firefox_env)

下面是Selemium启动firefox的源码，有时间补上注释

import osimport platformfrom subprocess import Popen, STDOUTfrom selenium.common.exceptions import WebDriverExceptionfrom selenium.webdriver.common import utilsimport timeclass FirefoxBinary(object):    NO_FOCUS_LIBRARY_NAME = "x_ignore_nofocus.so"    def __init__(self, firefox_path=None, log_file=None):        """        Creates a new instance of Firefox binary.        :Args:         - firefox_path - Path to the Firefox executable. By default, it will be detected from the standard locations.         - log_file - A file object to redirect the firefox process output to. It can be sys.stdout.                      Please note that with parallel run the output won't be synchronous.                      By default, it will be redirected to /dev/null.        """        self._start_cmd = firefox_path        # We used to default to subprocess.PIPE instead of /dev/null, but after        # a while the pipe would fill up and Firefox would freeze.        self._log_file = log_file or open(os.devnull, "wb")        self.command_line = None        if self._start_cmd is None:            self._start_cmd = self._get_firefox_start_cmd()        if not self._start_cmd.strip():          raise Exception("Failed to find firefox binary. You can set it by specifying the path to 'firefox_binary':\n\nfrom selenium.webdriver.firefox.firefox_binary import FirefoxBinary\n\n" +            "binary = FirefoxBinary('/path/to/binary')\ndriver = webdriver.Firefox(firefox_binary=binary)")        # Rather than modifying the environment of the calling Python process        # copy it and modify as needed.        self._firefox_env = os.environ.copy()        self._firefox_env["MOZ_CRASHREPORTER_DISABLE"] = "1"        self._firefox_env["MOZ_NO_REMOTE"] = "1"        self._firefox_env["NO_EM_RESTART"] = "1"    def add_command_line_options(self, *args):        self.command_line = args    def launch_browser(self, profile, timeout=30):        """Launches the browser for the given profile name.        It is assumed the profile already exists.        """        self.profile = profile        self._start_from_profile_path(self.profile.path)        self._wait_until_connectable(timeout=timeout)    def kill(self):        """Kill the browser.        This is useful when the browser is stuck.        """        if self.process:            self.process.kill()            self.process.wait()    def _start_from_profile_path(self, path):        self._firefox_env["XRE_PROFILE_PATH"] = path        if platform.system().lower() == 'linux':            self._modify_link_library_path()        command = [self._start_cmd, "-foreground"]        if self.command_line is not None:            for cli in self.command_line:                command.append(cli)        self.process = Popen(            command, stdout=self._log_file, stderr=STDOUT,            env=self._firefox_env)    def _wait_until_connectable(self, timeout=30):        """Blocks until the extension is connectable in the firefox."""        count = 0        while not utils.is_connectable(self.profile.port):            if self.process.poll() is not None:                # Browser has exited                raise WebDriverException("The browser appears to have exited "                      "before we could connect. If you specified a log_file in "                      "the FirefoxBinary constructor, check it for details.")            if count >= timeout:                self.kill()                raise WebDriverException("Can't load the profile. Profile "                      "Dir: %s If you specified a log_file in the "                      "FirefoxBinary constructor, check it for details."                      % (self.profile.path))            count += 1            time.sleep(1)        return True    def _find_exe_in_registry(self):        try:            from _winreg import OpenKey, QueryValue, HKEY_LOCAL_MACHINE, HKEY_CURRENT_USER        except ImportError:            from winreg import OpenKey, QueryValue, HKEY_LOCAL_MACHINE, HKEY_CURRENT_USER        import shlex        keys = (           r"SOFTWARE\Classes\FirefoxHTML\shell\open\command",           r"SOFTWARE\Classes\Applications\firefox.exe\shell\open\command"        )        command = ""        for path in keys:            try:                key = OpenKey(HKEY_LOCAL_MACHINE, path)                command = QueryValue(key, "")                break            except OSError:                try:                    key = OpenKey(HKEY_CURRENT_USER, path)                    command = QueryValue(key, "")                    break                except OSError:                    pass        else:            return ""        if not command:            return ""        return shlex.split(command)[0]    def _get_firefox_start_cmd(self):        """Return the command to start firefox."""        start_cmd = ""        if platform.system() == "Darwin":            start_cmd = "/Applications/Firefox.app/Contents/MacOS/firefox-bin"            # fallback to homebrew installation for mac users            if not os.path.exists(start_cmd):                start_cmd = os.path.expanduser("~") + start_cmd        elif platform.system() == "Windows":            start_cmd = (self._find_exe_in_registry() or                self._default_windows_location())        elif platform.system() == 'Java' and os._name == 'nt':            start_cmd = self._default_windows_location()        else:            for ffname in ["firefox", "iceweasel"]:                start_cmd = self.which(ffname)                if start_cmd is not None:                    break            else:                # couldn't find firefox on the system path                raise RuntimeError("Could not find firefox in your system PATH." +                    " Please specify the firefox binary location or install firefox")        return start_cmd    def _default_windows_location(self):        program_files = [os.getenv("PROGRAMFILES", r"C:\Program Files"),                         os.getenv("PROGRAMFILES(X86)", r"C:\Program Files (x86)")]        for path in program_files:            binary_path = os.path.join(path, r"Mozilla Firefox\firefox.exe")            if os.access(binary_path, os.X_OK):                return binary_path        return ""    def _modify_link_library_path(self):        existing_ld_lib_path = os.environ.get('LD_LIBRARY_PATH', '')        new_ld_lib_path = self._extract_and_check(            self.profile, self.NO_FOCUS_LIBRARY_NAME, "x86", "amd64")        new_ld_lib_path += existing_ld_lib_path        self._firefox_env["LD_LIBRARY_PATH"] = new_ld_lib_path        self._firefox_env['LD_PRELOAD'] = self.NO_FOCUS_LIBRARY_NAME    def _extract_and_check(self, profile, no_focus_so_name, x86, amd64):        paths = [x86, amd64]        built_path = ""        for path in paths:            library_path = os.path.join(profile.path, path)            if not os.path.exists(library_path):                os.makedirs(library_path)            import shutil            shutil.copy(os.path.join(os.path.dirname(__file__), path,              self.NO_FOCUS_LIBRARY_NAME),              library_path)            built_path += library_path + ":"        return built_path    def which(self, fname):        """Returns the fully qualified path by searching Path of the given        name"""        for pe in os.environ['PATH'].split(os.pathsep):            checkname = os.path.join(pe, fname)            if os.access(checkname, os.X_OK) and not os.path.isdir(checkname):                return checkname        return None