You need to make sure that the geckodriver executable is available in your PATH. Otherwise, Selenium will throw this error:
selenium.common.exceptions.WebDriverException: Message: 'geckodriver' executable needs to be in PATH.
The best way to fix this error is to use the webdriver-manager package. It will make sure that you have a valid geckodriver executable in PATH and if it is not available, it will download it automatically. You can install it using PIP:
$ pip install webdriver-manager
And use it in your Python code like this:
from selenium import webdriver
from selenium.webdriver.firefox.service import Service
from webdriver_manager.firefox import GeckoDriverManager
driver = webdriver.Firefox(service=Service(GeckoDriverManager().install()))
# Open Scrapingbee's website
driver.get("http://www.scrapingbee.com")
The code might take a second or two on the initial run as it has to download the geckodriver binary. Successive runs should be a lot faster.