explicit 0.1.3

Helper class to make working with Selenium explicit waits easier and more accessible

Explicit is designed to minimize or eleminate the common frustrations encountered when using Selenium on webpages with dynamicly loaded and/or javascript driven content. Typically, a developer will try to use the webdriver’s default find_element_by_<XPATH, CSS, ID, LINK TEXT, ETC> to locate an element, only to get hit with various exceptions like NoSuchElementException, StaleElementReferenceException, and so on.

Selenium includes several tools to address these limitations, most notibly implicit and explicit waits. While enabling the implicit wait is easy to do, it becomes increasingly problematic as scripts become more complex. Explicit waits offer a much more powerful alternative, giving the developer more fine tuned controls, but at the expense of added complexity.

The Explicit package abstracts away the complexities associated with explicit waits by wrapping commonly used functionality in an easy to use API.

Consider this example: You want to use Selenium to log into Github from the 404 page. You write a script like this to fill in the login credentials and click the login button:

from selenium import webdriver

driver = webdriver.Chrome()

try:
    driver.get("https://github.com/this/doesntexist")

    username_field = driver.find_element_by_id("login_field")
    username_field.click()
    username_field.send_keys("my_username")

    password_field = driver.find_element_by_id("password")
    password_field.click()
    password_field.send_keys("my_password")

    login_button = driver.find_element_by_css_selector("input.btn-primary")
    login_button.click()

finally:
    driver.quit()

When you run the program, however, you get an immediate exception:

(.venv35) ➜  explicit ✗ python example.py
Traceback (most recent call last):
File "example.py", line 9, in <module>
    username_field = driver.find_element_by_id("login_field")
<...>
    raise exception_class(message, screen, stacktrace)
selenium.common.exceptions.NoSuchElementException: Message: no such element: Unable to locate element: {"method":"id","selector":"login_field"}

The reason for the execption, which might not be readily apparent, is that the login modal on that page loads in after the page loads. When the script runs it attempts to immediately find the field element after control is returned from the driver.get call. Since the element isn’t in the DOM yet, Selenium throws the NoSuchElementException.

Explicit easily solves this by waiting for the element to load in:

from explicit import waiter
from explicit import ID, CSS
from selenium import webdriver

driver = webdriver.Chrome()

try:
    driver.get("https://github.com/this/doesntexist")

    username_field = waiter.find_element(driver, "login_field", by=ID)
    username_field.click()
    username_field.send_keys("my_username")

    password_field = waiter.find_element(driver, "password", by=ID)
    password_field.click()
    password_field.send_keys("my_password")

    login_button = waiter.find_element(driver, "input.btn-primary", by=CSS)
    login_button.click()
finally:
    driver.quit()

Additionally, you can use explicit to handle the writing:

from explicit import waiter
from explicit import ID, CSS
from selenium import webdriver

driver = webdriver.Chrome()

try:
    driver.get("https://github.com/this/doesntexist")

    waiter.find_write(driver, "login_field", "my_username", by=ID)

    waiter.find_write(driver, "password", "my_password", by=ID, send_enter=True)

finally:
    driver.quit()