Python Selenium: Closing a new tab with driver.close() is probably causing "no such window: target window already closed; web view not found" error

Question

Recently I have started working with multiple tabs in Selenium and I have encountered a strange problem. When I'm executing this code:

WebDriverWait(driver, 10).until(EC.number_of_windows_to_be(2))
driver.switch_to.window(driver.window_handles[-1])
time.sleep(1)
url_in_page_source= eu.look_for_url_in_page_source(
    page_html=driver.page_source,
    left_delimiter='placeholder',
    right_delimiter='placeholder'
)
driver.close()
driver.switch_to.window(driver.window_handles[0])
# time.sleep(10) # <--- this is fixing the error
return url_in_page_source

and immediately after the return statement when I'm trying to visit extracted url by driver.get() I'm getting this error:

Message: no such window: target window already closed
from unknown error: web view not found

However I have found out that adding a simple time.sleep(10) just before return statement is fixing the issue, but what is more strange to me - when I have tried to lower the wait time just below 10 secs the error is still existing. I have no idea why it is happening. Maybe I'm doing something wrong. I will be very grateful for any help and explanations.

Edit: Here's source code of the eu.look_for_url_in_page_source() as per @JeffC request

def look_for_url_in_page_source(page_html, left_url_delimiter, right_url_delimiter):
    print('Processing URL with f:look_for_url_in_page_source()')
    # extracts multiple URLs from page_source
    extracted_urls = []
    while True:
        # check if delimiters are present in page_html
        find_left_url_delimiter = page_html.find(left_url_delimiter)
        find_right_url_delimiter = page_html.find(right_url_delimiter)
        if find_left_url_delimiter == -1 or find_right_url_delimiter == -1:
            if len(extracted_urls) > 0:
                return extracted_urls
            print('f:look_for_url_in_page_source() was not able to get any text.')
            return False
        left_url_delimiter_pos = find_left_url_delimiter + len(left_url_delimiter)
        right_url_delimiter_pos = page_html[left_url_delimiter_pos:].find(right_url_delimiter) + left_url_delimiter_pos
        extracted_url = page_html[left_url_delimiter_pos:right_url_delimiter_pos].strip()
        extracted_urls.append(extracted_url)
        page_html = page_html[right_url_delimiter_pos:]

Answer 1

There are a lot many process involved in the process of closing a tab and switching to the parent Browsing Context which is beyond the scope of our naked eyes. Having said that, neither

driver.switch_to.window(driver.window_handles[-1])

is an ideal way to switch to the new tab, nor

driver.switch_to.window(driver.window_handles[0])

is an ideal way to switch to the parent tab.

You can find a detailed discussion on tab switching in Open web in new tab Selenium + Python

---

References

A few relevant discussions:

• "NoSuchWindowException: no such window: window was already closed" while switching tabs using Selenium and WebDriver through Python3