executable needs to be in path code example

Example 1: geckodriver' executable needs to be in path

from selenium import webdriver
driver = webdriver.Firefox(executable_path=r'your\path\geckodriver.exe')
driver.get('http://inventwithpython.com')

Example 2: Message: 'chromedriver' executable needs to be in PATH. Please see https://sites.google.com/a/chromium.org/chromedriver/home

You can download ChromeDriver here: https://sites.google.com/a/chromium.org/chromedriver/downloads

Then you have multiple options:

add it to your system path
put it in the same directory as your python script
specify the location directly via executable_path

driver = webdriver.Chrome(executable_path='C:/path/to/chromedriver.exe')

Example 3: Message: 'chromedriver' executable needs to be in PATH.

driver = webdriver.Chrome('/path/to/chromedriver')