Close Window

from selenium import webdriver
session = webdriver.Firefox()
original_window = session.window_handle
new_window = session.execute_script("return window.open()")
session.switch_to.window(new_window)
session.close()
session.switch_to.window(original_window)

using OpenQA.Selenium.Firefox;
namespace MDNWebDriverExamples
{
    class Example
    {
        public static void Main(string[] args)
        {
            FirefoxDriver session = new FirefoxDriver();
            string original_window = session.CurrentWindowHandle;// Optional if you want to store the handle in a variable
            session.ExecuteScript("window.open()");
            session.SwitchTo().Window(session.WindowHandles[1]); // Switch to the second window
            session.Close(); // Close current window
            session.SwitchTo().Window(session.WindowHandles[0]); // Switch back to the first window
        }
    }
}