Foreword:
Adding too many sleeps to the script will affect the execution speed of the script, although implicitly_wait() this method saves a lot of time to a certain extent.
But once some js on the page cannot be loaded (in fact, the interface elements have come out), the icon in the upper left corner keeps spinning, and it will wait for a while.
1. Explanation of parameters
1. There are three main parameters here:
class WebDriverWait(object):driver, timeout, poll_frequency
2.driver: Returns an instance of the browser, needless to say
3.timeout: the total duration of the timeout
4.poll_frequency: the interval time for looping to query, the default is 0.5 seconds
以下是源码的解释文档（案例一个是元素出现，一个是元素消失）
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).until(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())
"""
Second, the element appears: until ()
1. There is a lambda function in until, see the python documentation for this syntax
2. Take Baidu input box as an example
3. The element disappears: until_not()
1. Determine whether the element disappears, if it returns True, if not, it returns False
Note: This method has not been adjusted well, temporarily put it here
4. Reference code:
# coding:utf-8
from selenium import webdriver
from selenium.webdriver.support.wait import WebDriverWait
driver = webdriver.Firefox()
driver.get("http://www.baidu.com")
# Waiting time is 10 seconds, default Ask
WebDriverWait(driver, 10) once every 0.5 seconds .\ until_not(lambda x: x.find_element_by_id("kw").is_displayed()) print is_disappeared
Five, WebDriverWait source code
1.WebDriverWait mainly provides two methods, one is until(), the other is until_not()
The following is the annotation of the source code, interested friends can read it
# Licensed to the Software Freedom Conservancy (SFC) under one
# or more contributor license agreements. See the NOTICE file
# distributed with this work for additional information
# regarding copyright ownership. The SFC licenses this file
# to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance
# with the License. You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing,
# software distributed under the License is distributed on an
# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
# KIND, either express or implied. See the License for the
# specific language governing permissions and limitations
# under the License.
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).until(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 '<{0.__module__}.{0.__name__} (session="{1}")>'.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)