Element locators in page class in Selenium Python - Build an Automation Script

Verify login button is visible on the login page

Preconditions (2)

Step 1: Open the browser and navigate to 'https://example.com/login'

Step 2: Locate the login button using the page class locator

Step 3: Check if the login button is visible on the page

✅ Expected Result: The login button is visible on the login page

Automation Requirements - Selenium with Python

Assertions Needed:

Assert that the login button element is displayed

Best Practices:

Use a Page Object Model (POM) class to store element locators

Use explicit waits to wait for elements to be visible

Use By.ID or By.CSS_SELECTOR for locators instead of brittle XPath

Keep test code clean by separating page locators and test logic

Automated Solution

Selenium Python

from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC

class LoginPage:
    # Element locators stored as class variables
    LOGIN_BUTTON = (By.ID, 'login-button')

    def __init__(self, driver):
        self.driver = driver

    def is_login_button_visible(self):
        wait = WebDriverWait(self.driver, 10)
        login_button = wait.until(EC.visibility_of_element_located(self.LOGIN_BUTTON))
        return login_button.is_displayed()


def test_login_button_visibility():
    driver = webdriver.Chrome()
    driver.get('https://example.com/login')

    login_page = LoginPage(driver)
    assert login_page.is_login_button_visible(), 'Login button should be visible on login page'

    driver.quit()

The LoginPage class stores the login button locator as a class variable LOGIN_BUTTON using By.ID. This keeps locators organized and easy to maintain.

The method is_login_button_visible uses an explicit wait to wait up to 10 seconds for the login button to be visible. This avoids timing issues.

The test function test_login_button_visibility opens the browser, navigates to the login page, creates a LoginPage object, and asserts the login button is visible. Finally, it closes the browser.

This structure follows best practices by separating locators in a page class and using explicit waits and clear assertions.

Common Mistakes - 3 Pitfalls

Hardcoding XPath locators that are brittle

Not using explicit waits before checking element visibility

Mixing locators directly in test code instead of page class

Bonus Challenge

Now add data-driven testing with 3 different login page URLs to verify the login button visibility on each

Show Hint

Practice

1. What is the main purpose of using element locators in a page class in Selenium Python?

easy

A. To find web elements clearly and reuse them easily

B. To write complex test logic inside the page class

C. To store test data separately from the test scripts

D. To execute browser commands directly

Solution

1. Step 1: Understand the role of element locators

   Element locators help identify web elements on a page so tests can interact with them.

2. Step 2: Recognize the benefit of using a page class

   Storing locators in a page class allows easy reuse and keeps code clean.

3. Final Answer:

   To find web elements clearly and reuse them easily -> Option A

4. Quick Check:

   Element locators = reuse and clarity [OK]

Hint: Locators in page class = find elements + reuse [OK]

Common Mistakes:

• Confusing locators with test data storage
• Thinking page class runs browser commands
• Assuming locators hold test logic

2. Which of the following is the correct way to define a locator for a button with id 'submit' in a Selenium page class?

easy

A. submit_button = By('id', 'submit')

B. submit_button = By.ID('submit')

C. submit_button = ('id', submit)

D. submit_button = (By.ID, 'submit')

Solution

1. Step 1: Recall the correct locator tuple format

   Locators are tuples with By strategy and string value, e.g., (By.ID, 'value').

2. Step 2: Check each option's syntax

   submit_button = (By.ID, 'submit') uses (By.ID, 'submit'), which is correct. Others use wrong syntax or missing quotes.

3. Final Answer:

   submit_button = (By.ID, 'submit') -> Option D

4. Quick Check:

   Locator tuple = (By.ID, 'value') [OK]

Hint: Locator = (By.<STRATEGY>, 'value') tuple [OK]

Common Mistakes:

• Using By.ID('submit') instead of tuple
• Missing quotes around 'submit'
• Using wrong tuple structure

3. Given the locator login_button = (By.CSS_SELECTOR, 'button.login') in a page class, what will driver.find_element(*login_button) do?

medium

A. Cause a syntax error because of unpacking

B. Find the first button element with class 'login' on the page

C. Find all button elements with class 'login' on the page

D. Find an element by tag name 'button.login'

Solution

1. Step 1: Understand the locator tuple and unpacking

   The locator is a tuple (By.CSS_SELECTOR, 'button.login'). Using * unpacks it into two arguments.

2. Step 2: Know what find_element does

   find_element returns the first matching element, not all elements.

3. Final Answer:

   Find the first button element with class 'login' on the page -> Option B

4. Quick Check:

   find_element + CSS selector = first match [OK]

Hint: find_element finds first match, unpack locator tuple [OK]

Common Mistakes:

• Confusing find_element with find_elements
• Thinking unpacking causes syntax error
• Misunderstanding CSS selector as tag name

4. You have this locator in your page class: search_box = (By.NAME, 'q'). Your test code uses driver.find_element(search_box) and fails. What is the error and how to fix it?

medium

A. Error: Missing unpacking operator '*'. Fix: Use driver.find_element(*search_box)

B. Error: Wrong locator type. Fix: Change By.NAME to By.ID

C. Error: Locator value is incorrect. Fix: Change 'q' to 'search'

D. Error: find_element cannot use tuples. Fix: Use string locator only

Solution

1. Step 1: Identify the cause of failure

   driver.find_element expects two arguments, but passing a tuple without unpacking sends one argument.

2. Step 2: Apply the correct fix

   Use the unpacking operator * to pass locator as separate arguments: driver.find_element(*search_box).

3. Final Answer:

   Error: Missing unpacking operator '*'. Fix: Use driver.find_element(*search_box) -> Option A

4. Quick Check:

   Unpack locator tuple with * [OK]

Hint: Always unpack locator tuple with * in find_element [OK]

Common Mistakes:

• Not using * causes TypeError
• Changing locator type unnecessarily
• Assuming locator value is wrong

5. You want to create a page class locator for a link with text 'Home' that may appear as either an <a> tag or a <button> tag. Which locator is best to find it reliably?

hard

A. home_link = (By.LINK_TEXT, 'Home')

B. home_link = (By.CSS_SELECTOR, 'a.home, button.home')

C. home_link = (By.XPATH, "//a[text()='Home'] | //button[text()='Home']")

D. home_link = (By.ID, 'home')

Solution

1. Step 1: Understand the locator requirements

   The element can be either an <a> or <button> with text 'Home', so locator must cover both tags.

2. Step 2: Evaluate locator options

   home_link = (By.XPATH, "//a[text()='Home'] | //button[text()='Home']") uses XPath with OR (|) to match either tag by exact text, which is reliable. home_link = (By.LINK_TEXT, 'Home') only works for <a> tags. home_link = (By.CSS_SELECTOR, 'a.home, button.home') uses classes which may not exist. home_link = (By.ID, 'home') uses ID which is not given.

3. Final Answer:

   home_link = (By.XPATH, "//a[text()='Home'] | //button[text()='Home']") -> Option C

4. Quick Check:

   XPath OR matches multiple tags [OK]

Hint: Use XPath OR (|) to match multiple tag types [OK]

Common Mistakes:

• Using LINK_TEXT misses button tags
• Using CSS selectors without classes
• Assuming ID exists without confirmation