Selenium Python is one of the great tools for testing automation. These days most of the web apps are using AJAX techniques. When a page is loaded by the browser, the elements within that page may load at different time intervals. This makes locating elements difficult: if an element is not yet present in the DOM, a locate function will raise an ElementNotVisibleException exception. Using waits, we can solve this issue. Waiting provides some slack between actions performed – mostly locating an element or any other operation with the element. Selenium Webdriver provides two types of waits –
Implicit Waits
An implicit wait tells WebDriver to poll the DOM for a certain amount of time when trying to find any element (or elements) not immediately available. The default setting is 0. Once set, the implicit wait is set for the life of the WebDriver object. Let’s consider an example –
# import webdriver from selenium import webdriver driver = webdriver.Firefox() # set implicit wait time driver.implicitly_wait(10) # seconds # get url # get element after 10 seconds myDynamicElement = driver.find_element_by_id("myDynamicElement") |
This waits up to 10 seconds before throwing a TimeoutException unless it finds the element to return within 10 seconds. To check out how to practically implement Implicit Waits in Webdriver, checkout Implicit waits in Selenium Python
Explicit Waits
An explicit wait is a code you define to wait for a certain condition to occur before proceeding further in the code. The extreme case of this is time.sleep(), which sets the condition to an exact time period to wait. There are some convenience methods provided that help you write code that will wait only as long as required. Explicit waits are achieved by using webdriverWait class in combination with expected_conditions. Let’s consider an example –
# import necessary classes from selenium.webdriver.common.by import By from selenium.webdriver.support.ui import WebDriverWait from selenium.webdriver.support import expected_conditions as EC # create driver object driver = webdriver.Firefox() # A URL that delays loading try: # wait 10 seconds before looking for element element = WebDriverWait(driver, 10).until( EC.presence_of_element_located((By.ID, "myDynamicElement")) ) finally: # else quit driver.quit() |
This waits up to 10 seconds before throwing a TimeoutException unless it finds the element to return within 10 seconds. WebDriverWait by default calls the ExpectedCondition every 500 milliseconds until it returns successfully.
Expected Conditions –
There are some common conditions that are frequently of use when automating web browsers. For example, presence_of_element_located, title_is, ad so on. one can check entire methods from here – Convenience Methods. Some of them are –
- title_is
- title_contains
- presence_of_element_located
- visibility_of_element_located
- visibility_of
- presence_of_all_elements_located
- element_located_to_be_selected
- element_selection_state_to_be
- element_located_selection_state_to_be
- alert_is_present
To check out how to practically implement Implicit Waits in Webdriver, checkout Explicit waits in Selenium Python
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