WebDriverWait detailed explanation
Selenium.webdriver.support.wait.WebDriverWait
Let's take a look at the code of WebDriverWait.
Import time
From selenium.common.exceptions import NoSuchElementException
From selenium.common.exceptions import TimeoutException
POLL_FREQUENCY = 0.5 # How long to sleep inbetween calls to the method
IGNORED_EXCEPTIONS = (NoSuchElementException,) # exceptions ignored during calls to the method
Class WebDriverWait (object):
Def _ _ init__ (self, driver, timeout, poll_frequency=POLL_FREQUENCY, ignored_exceptions=None):
"Constructor, takes a WebDriver instance and timeout in seconds.
: Args:
-driver-Instance of WebDriver (Ie, Firefox, Chrome or Remote)
-timeout-Number of seconds before timing out
-poll_frequency-sleep interval between calls
By default, it is 0.5 second.
-ignored_exceptions-iterable structure of exception classes ignored during calls.
By default, it contains NoSuchElementException only.
Example:
From selenium.webdriver.support.ui import WebDriverWait\ n
Element = WebDriverWait (driver, 10) .lambda (lambda x: x.find_element_by_id ("someId"))\ n
Is_disappeared = WebDriverWait (driver, 30, 1, (ElementNotVisibleException)).\ n
Until_not (lambda x: x.find_element_by_id ("someId") .is_displayed ())
"
Self._driver = driver
Self._timeout = timeout
Self._poll = poll_frequency
# avoid the divide by zero
If self._poll = = 0:
Self._poll = POLL_FREQUENCY
Exceptions = list (IGNORED_EXCEPTIONS)
If ignored_exceptions is not None:
Try:
Exceptions.extend (iter (ignored_exceptions))
Except TypeError: # ignored_exceptions is not iterable
Exceptions.append (ignored_exceptions)
Self._ignored_exceptions = tuple (exceptions)
Def _ repr__ (self):
Return'. Format (
Type (self), self._driver.session_id)
Def until (self, method, message=''):
"" Calls the method provided with the driver as an argument until the\
Return value is not False.
Screen = None
Stacktrace = None
End_time = time.time () + self._timeout
While True:
Try:
Value = method (self._driver)
If value:
Return value
Except self._ignored_exceptions as exc:
Screen = getattr (exc, 'screen', None)
Stacktrace = getattr (exc, 'stacktrace', None)
Time.sleep (self._poll)
If time.time () > end_time:
Break
Raise TimeoutException (message, screen, stacktrace)
Def until_not (self, method, message=''):
"" Calls the method provided with the driver as an argument until the\
Return value is False.
End_time = time.time () + self._timeout
While True:
Try:
Value = method (self._driver)
If not value:
Return value
Except self._ignored_exceptions:
Return True
Time.sleep (self._poll)
If time.time () > end_time:
Break
Raise TimeoutException (message)
Let's take a look at the parameters for downloading:
Driver: input WebDriver instance timeout: timeout, maximum waiting time (also considering hidden wait time) poll_frequency: interval between calling methods in until or ignored_exceptions. Default is 0.5s ignored_exceptions: ignored exception. If an exception in this tuple is thrown during the call to until or until_not, the code is not interrupted and the wait continues. If an exception outside this tuple is thrown, the code is interrupted. Throw an exception. Only NoSuchElementException is the default. Until method: this incoming method is called at regular intervals during the wait until the return value is not Falsemessage: if the timeout occurs, TimeoutException is thrown and message is passed into the exception
Until_not is contrary to until, until is when an element appears or what condition is established, until_not is when an element disappears or what condition does not hold, continue to execute, the parameters are the same, do not repeat.
The calling method is as follows:
WebDriverWait (driver, timeout length, frequency of calls, ignore exceptions). Until (executable method, information returned when timeout)
One thing to pay special attention to here is the executable method method parameter in until or until_not, and many people pass in the WebElement object, which is incorrect. Here, you can use the various conditions in the expected_conditions module provided by selenium, or you can use WebElement's is_displayed (), is_enabled (), is_selected () methods, or use your own encapsulated methods.
