Selenium + Python：无法使用 Try & WebDriverWait 捕获 TimeoutException

Question

Python version: 3.10; Selenium Webdriver: Firefox; IDE: PyCharm 2021.3.2 (CE); OS: Fedora 35 VM

I am writing a python selenium script to scrape data from a website. I would like to navigate through a website, find an element & print it. I am able to do this when the element is present. My problem is that sometimes the element is not present & I get an exception. If the element is not present when I use this code:

 RemainDeductible = (WebDriverWait(driver, 10).until(EC.presence_of_element_located((By.ID, "b8-b36-Input_RemainAmtYr1"))).get_attribute("value"))

the script produces the following exception:

 Traceback (most recent call last):
  
 File "...PythonSeleniumScript.py", line 152, in <module>
    RemainDue = (WebDriverWait(driver, 10).until(EC.presence_of_element_located((By.ID, "b8-b36-Input_RemainAmtYr1"))).get_attribute("value"))

 File "/usr/local/lib/python3.10/site-packages/selenium/webdriver/support/wait.py", line 89, in until
    raise TimeoutException(message, screen, stacktrace)

 selenium.common.exceptions.TimeoutException: Message: 
Stacktrace:
WebDriverError@chrome://remote/content/shared/webdriver/Errors.jsm:183:5
NoSuchElementError@chrome://remote/content/shared/webdriver/Errors.jsm:395:5
element.find/</<@chrome://remote/content/marionette/element.js:300:16

If the Timeout Exception occurs I would like to catch the exception & set the "Remain Due" variable to the string "BLANK". I still get the following Timeout Exception if I use Try in my code as follows:

try:
    RemainDue = (WebDriverWait(driver, 5).until(EC.presence_of_element_located((By.ID, "b8-b36-Input_RemainAmtYr1"))).get_attribute("value"))
except TimeoutException:
    RemainDue = "BLANK"

I still get the Timeout Exception. I thought my code would catch the exception. Why is it not catching it???

 Traceback (most recent call last):
  
 File "...PythonSeleniumScript.py", line 155, in <module>
    RemainDue = (WebDriverWait(driver, 5).until(EC.presence_of_element_located((By.ID, "b8-b36-Input_RemainAmtYr1"))).get_attribute("value"))

  File "/usr/local/lib/python3.10/site-packages/selenium/webdriver/support/wait.py", line 89, in until

    raise TimeoutException(message, screen, stacktrace)

 selenium.common.exceptions.TimeoutException: Message: 
Stacktrace:
WebDriverError@chrome://remote/content/shared/webdriver/Errors.jsm:183:5
NoSuchElementError@chrome://remote/content/shared/webdriver/Errors.jsm:395:5
element.find/</<@chrome://remote/content/marionette/element.js:300:16

The relevant HTML for the element I am trying to locate is:

<input id="b8-b36-Input_RemainAmtYr1"
class="form-control OSFillParent" data-
input="" disabled="" type="text"
style="margin-top: 5px;" value="$10.50">
event

Of course the code does work when the element is present . My issue is that the code crashes with the Timeout Exception when the element is not present. When the Timeout Exception occurs how do I catch the Timeout Exception & set the "Remain Due" variable to the string "BLANK"?

Answer 1

I would suggest several things here:

1. instead of

except TimeoutException:

Try using

except:

I understand that it's preferable to catch a specific exception type rather any exception, but I will still advice doing that here.
2) I would suggest using visibility_of_element_located instead of presence_of_element_located since presence_of_element_located will wait for presence of such element on the page only while it may still not be completely rendered. While visibility_of_element_located will wait for much more mature element state, when it is visible.
So instead of

try:
    RemainDue = (WebDriverWait(driver, 5).until(EC.presence_of_element_located((By.ID, "b8-b36-Input_RemainAmtYr1"))).get_attribute("value"))
except TimeoutException:
    RemainDue = "BLANK"

I would suggest you using

try:
    RemainDue = (WebDriverWait(driver, 5).until(EC.visibility_of_element_located((By.ID, "b8-b36-Input_RemainAmtYr1"))).get_attribute("value"))
except:
    RemainDue = "BLANK"

Also make sure the id value of b8-b36-Input_RemainAmtYr1 is fixed, not changing.