2. Getting Started

2.1. Simple Usage

If you have installed Selenium Python bindings, you can start using it from Python like this.

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

driver = webdriver.Firefox()
driver.get("http://www.python.org")
assert "Python" in driver.title
elem = driver.find_element(By.NAME, "q")
elem.clear()
elem.send_keys("pycon")
elem.send_keys(Keys.RETURN)
assert "No results found." not in driver.page_source
driver.close()

The above script can be saved into a file (eg:- python_org_search.py), then it can be run like this:

python python_org_search.py

The python which you are running should have the selenium module installed.

2.2. Example Explained

The selenium.webdriver module provides all the WebDriver implementations. Currently supported WebDriver implementations are Firefox, Chrome, IE and Remote. The Keys class provide keys in the keyboard like RETURN, F1, ALT etc. The By class is used to locate elements within a document.

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

Next, the instance of Firefox WebDriver is created.

driver = webdriver.Firefox()

The driver.get method will navigate to a page given by the URL. WebDriver will wait until the page has fully loaded (that is, the “onload” event has fired) before returning control to your test or script. Be aware that if your page uses a lot of AJAX on load then WebDriver may not know when it has completely loaded:

driver.get("http://www.python.org")

The next line is an assertion to confirm that title has the word “Python” in it:

assert "Python" in driver.title

WebDriver offers a number of ways to find elements using the find_element method. For example, the input text element can be located by its name attribute using the find_element method and using By.NAME as its first parameter. A detailed explanation of finding elements is available in the Locating Elements chapter:

elem = driver.find_element(By.NAME, "q")

Next, we are sending keys, this is similar to entering keys using your keyboard. Special keys can be sent using the Keys class imported from selenium.webdriver.common.keys. To be safe, we’ll first clear any pre-populated text in the input field (e.g. “Search”) so it doesn’t affect our search results:

elem.clear()
elem.send_keys("pycon")
elem.send_keys(Keys.RETURN)

After submission of the page, you should get the result if there is any. To ensure that some results are found, make an assertion:

assert "No results found." not in driver.page_source

Finally, the browser window is closed. You can also call the quit method instead of close. The quit method will exit the browser whereas close will close one tab, but if just one tab was open, by default most browsers will exit entirely.:

driver.close()

2.3. Using Selenium to write tests

Selenium is mostly used for writing test cases. The selenium package itself doesn’t provide a testing tool/framework. You can write test cases using Python’s unittest module. The other options for a tool/framework are pytest and nose.

In this chapter, we use unittest as the framework of choice. Here is the modified example which uses the unittest module. This is a test for the python.org search functionality:

import unittest
from selenium import webdriver
from selenium.webdriver.common.keys import Keys
from selenium.webdriver.common.by import By

class PythonOrgSearch(unittest.TestCase):

    def setUp(self):
        self.driver = webdriver.Firefox()

    def test_search_in_python_org(self):
        driver = self.driver
        driver.get("http://www.python.org")
        self.assertIn("Python", driver.title)
        elem = driver.find_element(By.NAME, "q")
        elem.send_keys("pycon")
        elem.send_keys(Keys.RETURN)
        self.assertNotIn("No results found.", driver.page_source)


    def tearDown(self):
        self.driver.close()

if __name__ == "__main__":
    unittest.main()

You can run the above test case from a shell like this:

python test_python_org_search.py
.
----------------------------------------------------------------------
Ran 1 test in 15.566s

OK

The above result shows that the test has been successfully completed.

Note: To run the above test in IPython or Jupyter, you should pass a couple of arguments to the main function as shown below:

unittest.main(argv=['first-arg-is-ignored'], exit=False)

2.4. Walkthrough of the example

Initially, all the basic modules required are imported. The unittest module is a built-in Python module based on Java’s JUnit. This module provides the framework for organizing the test cases. The selenium.webdriver module provides all the WebDriver implementations. Currently supported WebDriver implementations are: Firefox, Chrome, IE and Remote. The Keys class provides keys in the keyboard like RETURN, F1, ALT etc. The By class is used to locate elements within a document.

import unittest
from selenium import webdriver
from selenium.webdriver.common.keys import Keys
from selenium.webdriver.common.by import By

The test case class is inherited from unittest.TestCase. Inheriting from the TestCase class is the way to tell unittest module that this is a test case:

class PythonOrgSearch(unittest.TestCase):

The setUp method is part of initialization. This method will get called before every test function which you are going to write in this test case class. Here you are creating an instance of a Firefox WebDriver.

def setUp(self):
    self.driver = webdriver.Firefox()

This is the test case method. The test case method should always start with characters test. The first line inside this method creates a local reference to the driver object created in setUp method.

def test_search_in_python_org(self):
    driver = self.driver

The driver.get method will navigate to a page given by the URL. WebDriver will wait until the page has fully loaded (that is, the “onload” event has fired) before returning control to your test or script. Be aware that if your page uses a lot of AJAX on load then WebDriver may not know when it has completely loaded:

driver.get("http://www.python.org")

The next line is an assertion to confirm that title has the word “Python” in it:

self.assertIn("Python", driver.title)

WebDriver offers a number of ways to find elements using the find_element method. For example, the input text element can be located by its name attribute using the find_element method. Detailed explanation of finding elements is available in the Locating Elements chapter:

elem = driver.find_element(By.NAME, "q")

Next, we are sending keys, this is similar to entering keys using your keyboard. Special keys can be sent using the Keys class imported from selenium.webdriver.common.keys:

elem.send_keys("pycon")
elem.send_keys(Keys.RETURN)

After submission of the page, you should get the result as per search if there is any. To ensure that some results are found, make an assertion:

self.assertNotIn("No results found.", driver.page_source)

The tearDown method will get called after every test method. This is a place to do all cleanup actions. In the current method, the browser window is closed. You can also call the quit method instead of close. The quit method will exit the entire browser, whereas close will close a tab, but if it is the only tab opened, by default most browsers will exit entirely.:

def tearDown(self):
    self.driver.close()

Final lines are some boiler plate code to run the test suite:

if __name__ == "__main__":
    unittest.main()

2.5. Using Selenium with remote WebDriver

To use the remote WebDriver, you should have the Selenium server running. To run the server, use this command:

java -jar selenium-server-standalone-2.x.x.jar

While running the Selenium server, you could see a message looking like this:

15:43:07.541 INFO - RemoteWebDriver instances should connect to: http://127.0.0.1:4444/wd/hub

The above line says that you can use this URL for connecting to the remote WebDriver. Here are some examples:

from selenium import webdriver

driver = webdriver.Remote(
   command_executor='http://127.0.0.1:4444/wd/hub',
   options=webdriver.ChromeOptions()
)

driver = webdriver.Remote(
   command_executor='http://127.0.0.1:4444/wd/hub',
   options=webdriver.FirefoxOptions()
)