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.