How to Check if any alert exists in selenium using Python

Question

I've written a selenium test case in python for a web page that manages users. Here, we can add a role for users and in case a role is already existing, then an alert araises. I'm not sure if the alert is a JavaScript alert or a webelement of the page itself. I want to automatically check the existence of the alert, because checking for the role from the entirety of the list is a waste of time and has an enormous load. I've tried this code:

browser = webdriver.Firefox()
browser.get("url")
browser.find_the_element_by_id("add_button").click()
try:
    alert = browser.switch_to_alert()
    alert.accept()
    print "alert accepted"
except:
    print "no alert"

But that didn't work. I got the error "UnexpectedAlertPresentException". I also tried this:

browser = webdriver.Firefox()
browser.get("url")
browser.find_the_element_by_id("add_button").click()
s = set(browser.window_handles)
s.remove(browser.current_window_handle)
browser.switch_to_window(s.pop()) 

And I still got the same error. Moreover, I checked the alert box with firebug to check if I can get access to its properties, but right click was disabled. I need an immediate solution. Even if its in Java or other languages, I'll figuring things out. Someone plz help me out.

Answer 1

This might work for you. It did for me. I set a conditional delay with WebDriverWait just before the point I expect the alert to popup. Then I switch to it, like this:

from selenium import webdriver
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC
from selenium.common.exceptions import TimeoutException

browser = webdriver.Firefox()
browser.get("url")
browser.find_the_element_by_id("add_button").click()

try:
    WebDriverWait(browser, 3).until(EC.alert_is_present(),
                                   'Timed out waiting for PA creation ' +
                                   'confirmation popup to appear.')

    alert = browser.switch_to.alert
    alert.accept()
    print("alert accepted")
except TimeoutException:
    print("no alert")

This command WebDriverWait(browser,3) will wait for atleast 3 seconds for a supported alert to appear.