Finding Elements
================
.. py:currentmodule:: marionette_driver.marionette
One of the most common and yet often most difficult tasks in Marionette is
finding a DOM element on a webpage or in the chrome UI. Marionette provides
several different search strategies to use when finding elements. All search
strategies work with both :func:`~Marionette.find_element` and
:func:`~Marionette.find_elements`, though some strategies are not implemented
in chrome scope.
In the event that more than one element is matched by the query,
:func:`~Marionette.find_element` will only return the first element found. In
the event that no elements are matched by the query,
:func:`~Marionette.find_element` will raise `NoSuchElementException` while
:func:`~Marionette.find_elements` will return an empty list.
Search Strategies
-----------------
Search strategies are defined in the :class:`By` class::
from marionette_driver import By
print(By.ID)
The strategies are:
* `id` - The easiest way to find an element is to refer to its id directly::
container = client.find_element(By.ID, 'container')
* `class name` - To find elements belonging to a certain class, use `class name`::
buttons = client.find_elements(By.CLASS_NAME, 'button')
* `css selector` - It's also possible to find elements using a `css selector`_::
container_buttons = client.find_elements(By.CSS_SELECTOR, '#container .buttons')
* `name` - Find elements by their name attribute (not implemented in chrome
scope)::
form = client.find_element(By.NAME, 'signup')
* `tag name` - To find all the elements with a given tag, use `tag name`::
paragraphs = client.find_elements(By.TAG_NAME, 'p')
* `link text` - A convenience strategy for finding link elements by their
innerHTML (not implemented in chrome scope)::
link = client.find_element(By.LINK_TEXT, 'Click me!')
* `partial link text` - Same as `link text` except substrings of the innerHTML
are matched (not implemented in chrome scope)::
link = client.find_element(By.PARTIAL_LINK_TEXT, 'Clic')
* `xpath` - Find elements using an xpath_ query::
elem = client.find_element(By.XPATH, './/*[@id="foobar"')
.. _css selector:
https://developer.mozilla.org/en-US/docs/Web/Guide/CSS/Getting_Started/Selectors
.. _xpath:
https://developer.mozilla.org/en-US/docs/Web/XPath
Chaining Searches
-----------------
In addition to the methods on the Marionette object, WebElement objects also
provide :func:`~WebElement.find_element` and :func:`~WebElement.find_elements`
methods. The difference is that only child nodes of the element will be searched.
Consider the following html snippet::
<div id="content">
<span id="main"></span>
</div>
<div id="footer"></div>
Doing the following will work::
client.find_element(By.ID, 'container').find_element(By.ID, 'main')
But this will raise a `NoSuchElementException`::
client.find_element(By.ID, 'container').find_element(By.ID, 'footer')
