Custom expected conditions in Selenium Python

Introduction

Sometimes, built-in wait conditions in Selenium do not fit your needs. Custom expected conditions let you create your own rules to wait for specific things on a webpage.

You want to wait until a specific text appears inside an element.

You need to check if a button becomes enabled before clicking.

You want to wait for a custom attribute to have a certain value.

You want to wait until a list has a certain number of items.

You want to combine multiple conditions into one wait.

Syntax

Selenium Python

from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC

class CustomCondition:
    def __init__(self, locator):
        self.locator = locator

    def __call__(self, driver):
        element = driver.find_element(*self.locator)
        # return True or element if condition met, else False or None
        return element if element.text == 'Expected Text' else False

Custom expected conditions are classes or functions that implement the __call__ method.

The __call__ method receives the driver and returns a truthy value when the condition is met, or False/None otherwise.

Examples

This custom condition waits until the given text appears inside the element found by the locator.

Selenium Python

class TextIsPresent:
    def __init__(self, locator, text):
        self.locator = locator
        self.text = text

    def __call__(self, driver):
        element = driver.find_element(*self.locator)
        return element if self.text in element.text else False

This function returns a custom condition that waits until an element's attribute equals a value.

Selenium Python

def element_has_attribute(locator, attribute, value):
    def _predicate(driver):
        element = driver.find_element(*locator)
        return element if element.get_attribute(attribute) == value else False
    return _predicate

Sample Program

This test script opens a webpage, waits up to 10 seconds for a button with ID 'submit-button' to become enabled, then prints confirmation.

Selenium Python

from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import WebDriverWait

class ButtonEnabled:
    def __init__(self, locator):
        self.locator = locator

    def __call__(self, driver):
        button = driver.find_element(*self.locator)
        return button if button.is_enabled() else False

# Setup driver (example with Chrome)
driver = webdriver.Chrome()
driver.get('https://example.com')

wait = WebDriverWait(driver, 10)
button_locator = (By.ID, 'submit-button')

# Wait until the button is enabled
button = wait.until(ButtonEnabled(button_locator))

print('Button is enabled:', button.is_enabled())

driver.quit()

Important Notes

Always return the element or a truthy value when the condition is met, so you can use it after waiting.

Return False or None if the condition is not met to keep waiting.

Custom conditions help make your tests more flexible and readable.

Summary

Custom expected conditions let you wait for exactly what you need on a page.

They are classes or functions with a __call__ method that Selenium calls repeatedly.

Use them to improve test reliability and clarity.

Practice

1. What is the main purpose of creating a custom expected condition in Selenium Python?

easy

A. To change the browser window size automatically

B. To speed up the browser loading time

C. To wait for a specific condition that is not covered by built-in expected conditions

D. To generate test reports automatically

Solution

1. Step 1: Understand built-in expected conditions

   Built-in expected conditions cover common waits like element visibility or clickability.

2. Step 2: Identify the need for custom conditions

   When a specific wait is not available, custom expected conditions let you define exactly what to wait for.

3. Final Answer:

   To wait for a specific condition that is not covered by built-in expected conditions -> Option C

4. Quick Check:

   Custom expected conditions = wait for custom needs [OK]

Hint: Custom conditions handle waits built-ins can't cover [OK]

Common Mistakes:

• Thinking custom conditions speed up browser loading
• Confusing custom conditions with browser resizing
• Assuming custom conditions generate reports

2. Which of the following is the correct way to define a custom expected condition class in Selenium Python?

easy

A. class MyCondition:
def __call__(self, driver):
return driver.title == 'Home'

B. def MyCondition(driver):
return driver.title == 'Home'

C. class MyCondition:
def call(self, driver):
return driver.title == 'Home'

D. class MyCondition:
def __init__(self, driver):
return driver.title == 'Home'

Solution

1. Step 1: Recall the special method for callable classes

   The method __call__ makes an instance callable like a function.

2. Step 2: Check method signature and return

   The __call__ method takes driver and returns a boolean or element to wait for.

3. Final Answer:

   class MyCondition:\n def __call__(self, driver):\n return driver.title == 'Home' -> Option A

4. Quick Check:

   Custom condition class needs __call__ method [OK]

Hint: Use __call__ method to make class callable [OK]

Common Mistakes:

• Using call instead of __call__ method
• Defining __init__ to return a value
• Defining a function instead of a class

3. Given this custom expected condition class, what will WebDriverWait(driver, 10).until(MyCondition()) return if the page title is 'Dashboard'?

class MyCondition:
    def __call__(self, driver):
        if driver.title == 'Dashboard':
            return True
        else:
            return False

medium

A. It will raise a TimeoutException immediately

B. It will return the driver object

C. It will return False immediately without waiting

D. It will wait until the title is 'Dashboard' and then return True

Solution

1. Step 1: Understand WebDriverWait with custom condition

   WebDriverWait calls the condition repeatedly until it returns a truthy value or timeout.

2. Step 2: Analyze the condition's return value

   If the title is 'Dashboard', __call__ returns True, so wait ends and returns True.

3. Final Answer:

   It will wait until the title is 'Dashboard' and then return True -> Option D

4. Quick Check:

   Condition returns True -> wait ends successfully [OK]

Hint: Wait ends when condition returns True [OK]

Common Mistakes:

• Thinking it raises TimeoutException immediately
• Assuming it returns False immediately
• Confusing return value with driver object

4. Identify the error in this custom expected condition class:

class ElementHasText:
    def __call__(self, driver):
        element = driver.find_element(By.ID, 'msg')
        if element.text:
            return element.text
        else:
            return False

medium

A. Missing import for By from selenium.webdriver.common.by

B. The __call__ method should return True or False only, not text

C. The class should inherit from WebDriverWait

D. The find_element method should be find_elements

Solution

1. Step 1: Check usage of By.ID in the code

   The code uses By.ID but does not import By, causing a NameError.

2. Step 2: Verify other parts of the code

   Returning element.text is valid for expected conditions; inheritance from WebDriverWait is not required.

3. Final Answer:

   Missing import for By from selenium.webdriver.common.by -> Option A

4. Quick Check:

   Using By requires importing it first [OK]

Hint: Always import By before using it [OK]

Common Mistakes:

• Assuming __call__ must return only True/False
• Thinking class must inherit WebDriverWait
• Confusing find_element with find_elements

5. You want to create a custom expected condition that waits until an element with ID 'status' has text containing the word 'Complete'. Which of these implementations is correct and efficient?

hard

A. class StatusComplete:
def __call__(self, driver):
element = driver.find_element(By.ID, 'status')
return element.text.startswith('Complete')

B. class StatusComplete:
def __call__(self, driver):
element = driver.find_element(By.ID, 'status')
return 'Complete' in element.text

C. class StatusComplete:
def __call__(self, driver):
element = driver.find_element(By.ID, 'status')
if element.text == 'Complete':
return True
else:
return False

D. class StatusComplete:
def __call__(self, driver):
element = driver.find_element(By.ID, 'status')
return element.text != ''

Solution

1. Step 1: Understand the requirement

   We want to wait until the text contains the word 'Complete' anywhere inside.

2. Step 2: Analyze each option's condition

   class StatusComplete: def __call__(self, driver): element = driver.find_element(By.ID, 'status') return 'Complete' in element.text checks if 'Complete' is in element.text, which matches the requirement exactly and returns a boolean.

3. Step 3: Compare other options

   class StatusComplete: def __call__(self, driver): element = driver.find_element(By.ID, 'status') if element.text == 'Complete': return True else: return False checks exact equality, which is too strict. class StatusComplete: def __call__(self, driver): element = driver.find_element(By.ID, 'status') return element.text.startswith('Complete') checks startswith, which is partial. class StatusComplete: def __call__(self, driver): element = driver.find_element(By.ID, 'status') return element.text != '' only checks non-empty text, which is too broad.

4. Final Answer:

   class StatusComplete:\n def __call__(self, driver):\n element = driver.find_element(By.ID, 'status')\n return 'Complete' in element.text -> Option B

5. Quick Check:

   Use 'in' to check substring presence [OK]

Hint: Use 'in' operator to check substring in text [OK]

Common Mistakes:

• Checking exact equality instead of substring
• Using startswith instead of contains
• Checking only for non-empty text