First: it is only warning, not error.

In my version 3.141.0 I can use both methods

from selenium import webdriver

driver = webdriver.Chrome() # Firefox()

driver.find_elements_by_css_selector(...)
driver.find_elements_by_xpath(...)
# etc.

and

from selenium import webdriver
from selenium.webdriver.common.by import By

driver = webdriver.Chrome() # Firefox()

driver.find_elements(By.CSS_SELECTOR, ...)
driver.find_elements(By.XPATH, ...)
# etc.

but it seems they plan to remove functions find_elements_by_... in the future (in versions 4.x) and now find_elements_by_... still works but it shows warning that you should use second method find_elements(By.CSS_SELECTOR, ...).

You could use module warnings to hide these warnings but better start using only second method.

BTW:

In source code for find_elements_by_css_selector you can see it runs warning.warn(...) and next it runs find_elements(By.CSS_SELECTOR, ...)

To check what version you use

import selenium

print(selenium.__version__)

Only using class names is not sufficient in your case.

• By.cssSelector(".ban") has 15 matching nodes
• By.cssSelector(".hot") has 11 matching nodes
• By.cssSelector(".ban.hot") has 5 matching nodes

Therefore you need more restrictions to narrow it down. Option 1 and 2 below are available for CSS selector, 1 might be the one that suits your needs best.

Option 1: Using list items' index (CssSelector or XPath)

Limitations

• Not stable enough if the site's structure changes

Example:

driver.FindElement(By.CssSelector("#rightbar > .menu > li:nth-of-type(3) > h5"));
driver.FindElement(By.XPath("//*[@id='rightbar']/ul/li[3]/h5"));

Option 2: Using Selenium's FindElements, then index them. (CssSelector or XPath)

Limitations

• Not stable enough if a site's structure changes
• Not the native selector's way

Example:

// Note that By.CssSelector(".ban.hot") and //*[contains(@class, 'ban hot')] are different, but doesn't matter in your case
IList<IWebElement> hotBanners = driver.FindElements(By.CssSelector(".ban.hot"));
IWebElement banUsStates = hotBanners[3];

Option 3: Using text (XPath only)

Limitations

• Not for multilanguage sites
• Only for XPath, not for Selenium's CssSelector

Example:

driver.FindElement(By.XPath("//h5[contains(@class, 'ban hot') and text() = 'us states']"));

Option 4: Index the grouped selector (XPath only)

Limitations

• Not stable enough if the site's structure changes
• Only for XPath, not CssSelector

Example:

driver.FindElement(By.XPath("(//h5[contains(@class, 'ban hot')])[3]"));

Option 5: Find the hidden list items link by href, then traverse back to h5 (XPath only)

Limitations

• Only for XPath, not CssSelector
• Low performance
• Tricky XPath

Example:

driver.FindElement(By.XPath(".//li[.//ul/li/a[contains(@href, 'geo.craigslist.org/iso/us/al')]]/h5"));