Find element by CSS selector in Selenium Python - Build an Automation Script

Locate and verify element using CSS selector

Preconditions (2)

Step 1: Open the target web page in the browser.

Step 2: Locate the element using the CSS selector '#submit-button.btn-primary'.

Step 3: Verify that the element is displayed on the page.

✅ Expected Result: The element with id 'submit-button' and class 'btn-primary' is found and visible on the page.

Automation Requirements - Selenium with Python

Assertions Needed:

Assert the element is found using the CSS selector.

Assert the element is visible (displayed) on the page.

Best Practices:

Use explicit waits to wait for the element to be present and visible.

Use By.CSS_SELECTOR locator strategy.

Avoid hardcoded sleeps.

Handle exceptions if element is not found.

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

# Initialize the WebDriver (e.g., Chrome)
driver = webdriver.Chrome()

try:
    # Open the target web page
    driver.get('https://example.com')  # Replace with actual URL

    # Wait up to 10 seconds for the element to be visible
    wait = WebDriverWait(driver, 10)
    element = wait.until(EC.visibility_of_element_located((By.CSS_SELECTOR, '#submit-button.btn-primary')))

    # Assert the element is displayed
    assert element.is_displayed(), "Element is not visible on the page"

finally:
    # Close the browser
    driver.quit()

This script starts by importing necessary Selenium modules.

It opens the browser and navigates to the target page.

Using WebDriverWait with visibility_of_element_located ensures the script waits until the element matching the CSS selector #submit-button.btn-primary is visible.

The assertion element.is_displayed() confirms the element is visible on the page.

Finally, the browser is closed to clean up.

This approach avoids using fixed waits and uses best practices for locating elements by CSS selector.

Common Mistakes - 4 Pitfalls

Using driver.find_element without waits

{'mistake': 'Using incorrect CSS selector syntax', 'why_bad': "The element won't be found if the selector is wrong.", 'correct_approach': "Use valid CSS selector syntax, e.g., '#id.class' for element with id and class."}

Using hardcoded sleep instead of waits

Not handling exceptions when element is missing

Bonus Challenge

Now add data-driven testing with 3 different CSS selectors to verify multiple elements.

Show Hint

Practice

1. Which method is used in Selenium Python to find an element by CSS selector?

easy

A. driver.find_element_by_name("selector")

B. driver.find_element(By.CSS_SELECTOR, "selector")

C. driver.find_element_by_xpath("selector")

D. driver.find_element_by_id("selector")

Solution

1. Step 1: Understand Selenium element finding methods

   Selenium provides different methods to find elements, including by ID, name, XPath, and CSS selector.

2. Step 2: Identify the correct method for CSS selector

   The method to find by CSS selector is driver.find_element(By.CSS_SELECTOR, "selector").

3. Final Answer:

   driver.find_element(By.CSS_SELECTOR, "selector") -> Option B

4. Quick Check:

   Find element by CSS selector = driver.find_element(By.CSS_SELECTOR, "selector") [OK]

Hint: Use By.CSS_SELECTOR with find_element for CSS selectors [OK]

Common Mistakes:

• Using find_element_by_id for CSS selectors
• Confusing XPath with CSS selector method
• Using deprecated find_element_by_* methods

2. Which of the following is the correct syntax to find an element with class name "btn-primary" using CSS selector in Selenium Python?

easy

A. driver.find_element(By.CSS_SELECTOR, ".btn-primary")

B. driver.find_element(By.CSS_SELECTOR, "#btn-primary")

C. driver.find_element(By.CSS_SELECTOR, "btn-primary")

D. driver.find_element(By.CSS_SELECTOR, "*btn-primary")

Solution

1. Step 1: Recall CSS selector for class names

   In CSS selectors, a class is selected by prefixing the class name with a dot (.)

2. Step 2: Match the correct syntax

   To select class "btn-primary", use ".btn-primary" inside find_element.

3. Final Answer:

   driver.find_element(By.CSS_SELECTOR, ".btn-primary") -> Option A

4. Quick Check:

   Class selector = .classname [OK]

Hint: Use dot (.) before class name in CSS selector [OK]

Common Mistakes:

• Using # instead of . for class selectors
• Omitting the dot before class name
• Using invalid wildcard * before class name

3. What will the following Selenium Python code select?

element = driver.find_element(By.CSS_SELECTOR, "div#main > ul.items > li.active")

medium

A. The first <li> element with class 'active' inside <ul> with class 'items' inside <div> with id 'main'

B. All <li> elements inside any <ul> inside any <div>

C. The <div> element with id 'main' only

D. The <ul> element with class 'items' only

Solution

1. Step 1: Break down the CSS selector

   The selector targets a
2. element with class 'active' that is a direct child of a <ul> with class 'items', which is a direct child of a <div> with id 'main'.

3. Step 2: Understand the element selected

   It selects the first matching
4. element with class 'active' inside the specified structure.

5. Final Answer:

   The first <li> element with class 'active' inside <ul> with class 'items' inside <div> with id 'main' -> Option A

6. Quick Check:

   CSS selector matches nested elements exactly [OK]

Hint: Read CSS selector from right to left for nested elements [OK]

Common Mistakes:

• Thinking it selects all <li> elements, not just with class 'active'
• Ignoring the direct child (>) combinators
• Confusing id (#) and class (.) selectors

4. Identify the error in this Selenium Python code snippet:

element = driver.find_element(By.CSS_SELECTOR, "#content .item[active]")

medium

A. The ID selector #content should be a class selector

B. The method find_element does not accept CSS selectors

C. The CSS selector should use double quotes inside single quotes

D. The attribute selector [active] is missing an equals sign and value

Solution

1. Step 1: Analyze the attribute selector syntax

   The selector uses [active] which means attribute 'active' must be present, but usually attributes require a value like [active="true"].

2. Step 2: Identify the correct attribute selector format

   To check for attribute presence only, [active] is valid, but if a value is expected, it must be [active="value"]. Here, likely a value is missing.

3. Final Answer:

   The attribute selector [active] is missing an equals sign and value -> Option D

4. Quick Check:

   Attribute selectors need correct syntax [OK]

Hint: Attribute selectors need = and value unless checking presence only [OK]

Common Mistakes:

• Assuming [active] always works without value
• Confusing ID (#) and class (.) selectors
• Using wrong quotes inside CSS selector string

5. You want to find all <input> elements inside a form with id "loginForm" that have both classes "input-field" and "required". Which CSS selector should you use with Selenium Python's find_elements method?

hard

A. "form#loginForm input#input-field#required"

B. "form#loginForm input .input-field .required"

C. "form#loginForm input.input-field.required"

D. "form#loginForm > input > .input-field > .required"

Solution

1. Step 1: Understand CSS selector for multiple classes

   To select elements with multiple classes, chain class selectors without spaces, e.g., .input-field.required.

2. Step 2: Combine with tag and parent selectors

   Use form#loginForm to select the form by id, then space to select descendants, then input.input-field.required for inputs with both classes.

3. Final Answer:

   "form#loginForm input.input-field.required" -> Option C

4. Quick Check:

   Multiple classes chained without spaces [OK]

Hint: Chain multiple classes without spaces in CSS selector [OK]

Common Mistakes:

• Adding spaces between multiple classes (selects descendants instead)
• Using multiple IDs on one element (invalid)
• Using child combinator (>) incorrectly for nested elements