Python Bindings

Dave Hunt edited this page Nov 28, 2016 · 8 revisions

Installation

Selenium officially supports python 2.7 and 3.5, however other versions should also work.

The latest official release is available on the Python Package Index. It's a good practice to install python packages into virtual environments rather than in your global site packages. To install this using pip, run the following command:

pip install selenium

Usage

Importing the module is performed by entering the following in your python shell:

Firefox

from selenium import webdriver
driver = webdriver.Firefox()

Google Chrome

from selenium import webdriver
driver = webdriver.Chrome()

Remote

from selenium import webdriver
driver = webdriver.Remote(browser_name="firefox", platform="any")

Internet Explorer

from selenium import webdriver
driver = webdriver.Ie()

Microsoft Edge

from selenium import webdriver
driver = webdriver.Edge()

Safari

from selenium import webdriver
driver = webdriver.Safari()

Documentation

The documentation is available online here and can by built locally using the command tox -e docs.

Interactive

Alternatively use your python shell to view all commands available to you, after importing perform:

dir(webdriver)

To view the docstrings (documentation text attached to a function or method), perform

print('functionname'.__doc__)

Where functionname is the function you wish to view more information on. For example,

print(selenium.open.__doc__)

Comparison with Java Bindings

Here is a summary of the major differences between the python and Java bindings.

Function Names

Function names separate compound terms with underscores, rather than using Java's camelCase formatting. For example, in python title is the equivalent of getTitle() in Java.

Flatter Structures

To reflect pythonic behavior of flat object hierarchies the python bindings e.g. find_element_by_xpath("//h1") rather than findElement(By.xpath("//h1")); but it does give you the freedom of doing find_element(by=By.XPATH, value='//h1')

Development

To install the latest unreleased version, clone https://github.com/SeleniumHQ/selenium and run the following commands from the repository root directory:

./go py_prep_for_install_release
python setup.py install

Tests

When developing Selenium, it is recommended you run the tests before and after making any changes to the code base. To perform these tests, you will first need to install Tox.

By default, running tox will attempt to execute all of the defined environments. This means the tests for python 2.7 and 3.5 will run for each of the supported drivers. This is most likely not what you want, as some drivers will not run on certain platforms. It is therefore recommended that you specify the environments you wish to execute. To list all environments available, run tox -l, and to execute a single environment, use tox -e.

As an example, this command will run the tests for Firefox against python 2.7:

tox -e py27-firefox

The tests are executed using pytest, and you can pass positional arguments through Tox by specifying -- before them. In addition to other things, this allows you to filter tests. For example, to run a single test file:

tox -e py27-firefox -- py/test/selenium/webdriver/common/visibility_tests.py

To run a single test, you can use the keyword filter, such as:

tox -e py27-firefox -- -k testShouldShowElementNotVisibleWithHiddenAttribute

Expected Failures

Unfortunately, there will be some tests that are expected to fail due to known issues. You can mark these tests using the standard pytest methods, however if the test uses the driver fixture to run against multiple drivers, this will mark the tests for all of those drivers. If a test is only expected to fail in a subset of drivers, you can extend the xfail mark with the name of the driver. For example, to mark a test as expected to fail in Chrome and Firefox (but pass using any other driver):

import pytest

@pytest.mark.xfail_chrome
@pytest.mark.xfail_firefox
def test_something(driver):
   assert something is True

All of the same arguments from pytest's xfail mark are available to these extended marks. Wherever possible you should provide a reason with a reference to the raised issue/bug. If the test raises an unexpected exception you should also provide the raises argument, as this will still cause a failure if the test starts failing for another reason.

If the expected failure is dependent on the platform, you should also include the condition argument so that the test will be allowed to pass on other environments. For example, to mark a test as expected to fail when run against Firefox on macOS:

import sys
import pytest
from selenium.common.exceptions import WebDriverException

@pytest.mark.xfail_firefox(
    condition=sys.platform == 'darwin',
    reason='https://myissuetracker.com/issue?id=1234',
    raises=WebDriverException
def test_something(driver):
   assert something is True

You should avoid using imperative xfail as these will never allow the test an opportunity to unexpectedly pass (when the issue is resolved).

We also recommend against using skip unless there is good reason. If your test failure causes a hang or some other undesirable side-effect you can pass run=False to the xfail mark.

To run expected failures locally, pass the --runxfail command line option to pytest. If you want to run all expected failures for a specific driver you can do this by filtering on the xfail mark:

tox -e py27-firefox -- -m xfail_firefox --runxfail

Releases

To perform a release you will need to be a maintainer of the package on PyPI. Before pushing a new release you will need to update the version number and change log. The version number is in the form of X.Y.Z, where X.Y is taken from the latest GitHub release, and Z increments for each release.

When you're ready, the release can be made by running the following command:

./go py_release