Python selenium : Explicitly wait for one of two elements to be loaded

Question

Is there a way using which I can wait for one of two elements to get loaded in selenium. I am using explicit waits and so far, haven't been able to figure out the solution.

Simply doing

WebDriverWait(driver,5).until(lambda driver : driver.find_element(By.ID,"a") or driver.find_element(By.ID,"b"))

doesn't seem to work. It just looks for element with id ="a".

Thanks!

Answer 1

find_element raises NoSuchElementException exception if no element is found.

If element with the id a does not exist, driver.find_element(By.ID,"a") will raises the exception and the driver.find_element(By.ID,"b") will not be executed.

A simple way to solve the problem is using find_elements which return empty list instead of raising the exception:

WebDriverWait(driver,5).until(
    lambda driver: driver.find_elements(By.ID,"a") or driver.find_elements(By.ID,"b"))

Answer 2

As falsetru explained if your first find_element call fails to find an element, it will raise NoSuchElementException and the 2nd part of your test won't execute.

I would suggest using a CSS selector that matches either IDs you are looking for:

WebDriverWait(driver, 5).until(
    lambda driver : driver.find_element_by_css_selector("#a, #b"))

This has an advantage over performing two find_elements calls becayse this will make only one roundtrip between your Selenium client (your script) and the Selenium server. This should always be faster than performing two find_elements calls. When performing tests locally, the difference won't be much but if you perform tests remotely, for instance using Sauce Labs or Browser Stack, the difference will be significant.