Wait for class to exist before continuing with selenium in Firefox

Question

I'm trying to make selenium wait until a certain class is able to be found on a page, I've tried several bits of code but nothing is working

Trying the following:

while not firefox.find_element_by_css_selector('.but selected'):
    print "test"
    time.sleep(1)

Returns

selenium.common.exceptions.NoSuchElementException: Message: Unable to locate element

Trying the following:

while not firefox.find_element_by_class_name('but selected'):
    print "test"
    time.sleep(1)

Returns:

selenium.common.exceptions.InvalidSelectorException: Message: The given selector but selected is either invalid or does not result in a WebElement. The following error occurred: InvalidSelectorError: Compound class names not permitted

Any idea what I am doing wrong and how to fix it?

Answer 1

You could try explicit-waits. Here is a small example:

#!/usr/bin/env python
# -*- coding: utf-8 -*-

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
from selenium.common.exceptions import TimeoutException


def test(url):
    wait_for_element = 30  # wait timeout in seconds
    firefox = webdriver.Firefox()
    firefox.get(url)

    try:
        WebDriverWait(firefox, wait_for_element).until(
            EC.element_to_be_clickable((By.CLASS_NAME, "but selected'")))
    except TimeoutException as e:
        print("Wait Timed out")
        print(e)

if __name__ == '__main__':
    test("http://www.python.org")