selenium.common.exceptions.SessionNotCreatedException: Message: Unable to find a matching set of capabilities with Firefox 46 through Selenium

Question

I must have some versions here that don't match up since I can't get Selenium with Python to fire up a Firefox web browser. I'm using an older version of Firefox because other people in here have the same old version of Python and for them the old version of Firefox works best.

Code:

from selenium import webdriver
from selenium import common
from selenium.webdriver import ActionChains
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
from selenium.common.exceptions import NoSuchElementException
from selenium.webdriver.common.desired_capabilities import DesiredCapabilities
driver=webdriver.Firefox(capabilities=DesiredCapabilities.FIREFOX)

Error:

Traceback (most recent call last):
  File "scrapeCommunitySelenium.py", line 13, in <module>
    driver=webdriver.Firefox(capabilities=DesiredCapabilities.FIREFOX)
  File "/Library/Python/2.7/site-packages/selenium/webdriver/firefox/webdriver.py", line 158, in __init__
    keep_alive=True)
  File "/Library/Python/2.7/site-packages/selenium/webdriver/remote/webdriver.py", line 154, in __init__
    self.start_session(desired_capabilities, browser_profile)
  File "/Library/Python/2.7/site-packages/selenium/webdriver/remote/webdriver.py", line 243, in start_session
    response = self.execute(Command.NEW_SESSION, parameters)
  File "/Library/Python/2.7/site-packages/selenium/webdriver/remote/webdriver.py", line 311, in execute
    self.error_handler.check_response(response)
  File "/Library/Python/2.7/site-packages/selenium/webdriver/remote/errorhandler.py", line 237, in check_response
    raise exception_class(message, screen, stacktrace)
selenium.common.exceptions.SessionNotCreatedException: Message: Unable to find a matching set of capabilities

Version info:

• Python 2.7.10
• Selenium 3.8.0
• Firefox 46.0
• GeckoDriver 0.19.1 (It's in a folder which is in my PATH environment variable)
• MacOS 10.12.6

Answer 1

As you are using Selenium 3.8.0 you have to use GeckoDriver as a mandatory. But again as you are using Firefox v46.0 you have to set the capability marionette as False through DesiredCapabilities() as follows :

from selenium import webdriver
from selenium.webdriver.common.desired_capabilities import DesiredCapabilities

cap = DesiredCapabilities().FIREFOX
cap["marionette"] = False
browser = webdriver.Firefox(capabilities=cap, executable_path="C:\\path\\to\\geckodriver.exe")
browser.get('http://google.com/')
browser.quit()

Answer 2

If you're going to use Geckodriver, you definitely need to use a newer version of Firefox. Frex: https://github.com/mozilla/geckodriver/releases/tag/v0.19.0 lists FF55 or greater.

If you plan on using FF46, don't use geckodriver. Update your capabilities to have marionette set to False:

caps = DesiredCapabilities.FIREFOX.copy()
caps['marionette'] = False
driver=webdriver.Firefox(capabilities=caps)

Answer 3

I had this issue on my MacOS 10.5 Catalina. What I did: 1. Installed the geckodriver using brew install geckodriver 2. Deleted/uninstalled my existing(OLD) Firefox browser (v.46) and installed v70. 3. tried:

from selenium import webdriver
browser = webdriver.Firefox()
browser.get('http://google.com')

The above worked fine with no errors, by launching Firefox and loading google.com