浏览器更改时，Python Selenium无法找到元素

Question

I'm writing a script to auto fill some fields with Selenium. I'm running into problems where if the script clicks on a button that navigates from the original url, then Python can't find the elements on the new page.

For example: If I have selenium navigate to this landing page first ( https://www.emedny.org ) and click on the log in for ePaces, and then try to fill out the form, I get an error. This code is what I run:

from selenium import webdriver

browser = webdriver.Chrome(path)

keyed_path = r'https://www.emedny.org'
browser.get(keyed_path)

epaces_login = browser.find_element_by_css_selector('#targetContainer > a:nth-child(3)')
epaces_login.click()

username = browser.find_element_by_id('Username')
username.send_keys('test')

This code opens up https://www.emedny.org , clicks on a button which takes us to a log in page ( https://www.emedny.org/epaces ), and is supposed to enter in a username on the page. However, I get this error:

NoSuchElementException: no such element: Unable to locate element: {"method":"id","selector":"Username"}
  (Session info: chrome=56.0.2924.87)
  (Driver info: chromedriver=2.29.461591 (62ebf098771772160f391d75e589dc567915b233),platform=Windows NT 6.3.9600 x86_64)

But, if I skip the landing page and open up the log in page directly, like in this code:

from selenium import webdriver

browser = webdriver.Chrome(path)

keyed_path = r'https://www.emedny.org/epaces'
browser.get(keyed_path)

username = browser.find_element_by_id('Username')
username.send_keys('test')

Then the code runs well, and updates the username field as expected. It seems as though Selenium might be searching for that id on the opening url only .

Here's the HTML for the username field:

<input name="Username" type="text" maxlength="8" id="Username" class="inputText" size="13" onchange="javascript:validate(this)">

Any suggestions? I've tried id, XPath, css selector, name, etc. Same error each time.

EDIT: The link that selenium clicks first opens up a new tab. Could that be part of the issue?

Answer 1

I figured it out. It's because the link being clicked on opened up a new tab. Selenium was searching for the elements on the previous tab. I used window_handles and switch_to_window like this:

browser = webdriver.Chrome(path)


keyed_path = r'https://www.emedny.org'
browser.get(keyed_path)

print(browser.window_handles)

epaces_login = browser.find_element_by_css_selector('#targetContainer > a:nth-child(3)')
epaces_login.click()


browser.switch_to_window(browser.window_handles[1])

username = browser.find_element_by_id('Username')

username.send_keys('test')