Selenium Python does not close the child window - python-3.x

Question

I have webpage which open new browser window on click. I am able to get 2 handles however driver.close() always closes the first/main window.
from selenium import webdriver
import time
driver = webdriver.Chrome()
driver.get("file:///D:/blackhole/print.html")
han = driver.window_handles
print("handles:", han) # gets 1 handle
time.sleep(2)
click_btn = driver.find_element_by_link_text('Print')
click_btn.click()
han = driver.window_handles
print("handles:", han) # gets 2 handles
driver.switch_to_window = han[1] # first element is always first window handle
driver.close() # main window close
Below webpage code which invokes new window
<a href="print.html"
onclick="window.open('popprint.html',
'newwindow',
'width=300,height=250');
return false;"
>Print</a>
Same behaviour for Firefox as well.
Python 3.6.7

Answer 1

Selenium is unable to close the active window i.e the newly opened window because practically you havn't switched to the newly opened window in a clean way.
Solution
A few words about Tab/Window switching/handling:
switch_to_window(window_name) is deprecated for quite some time now and you need to use driver.switch_to.window
Always keep track of the Parent Window handle so you can traverse back later if required as per your usecase.
Always use WebDriverWait with expected_conditions as number_of_windows_to_be(num_windows) before switching between Tabs/Windows.
Always keep track of the Child Window handles so you can traverse whenever required.
Always use WebDriverWait with expected_conditions as title_contains("partial_page_title") before extracting the Page Title.
Here is your own code with some minor tweaks mentioned above:
from selenium import webdriver
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC
driver = webdriver.Firefox(executable_path=r'C:\WebDrivers\geckodriver.exe')
driver.get("file:///D:/blackhole/print.html")
parent_han = driver.window_handles
driver.find_element_by_link_text('Print').click()
WebDriverWait(driver, 10).until(EC.number_of_windows_to_be(2))
all_han = driver.window_handles
new_han = [x for x in all_han if x != parent_han][0]
driver.switch_to.window(new_han)
driver.close()
You can find a detailed discussion in Selenium Switch Tabs

Answer 2

driver.close() only closes the current window.
To close all Windows and quit the webdriver, call driver.quit() instead.