"driver.implicitly_wait(20)" 和 "WebDriverWait(driver, 20)" 之间的区别

Question

我有两个与等待相关的问题。 首先，请解释一下这两种waiting方法有什么区别

WebDriverWait(driver, 20).until(EC.presence_of_element_located((By.ID,
'twotabsearchtextbox')))
# and this
driver.implicitly_wait(20)

注意之前我写了个代码看看有什么不同，但是我并不清楚有什么不同 你写的代码

from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.support import expected_conditions as EC
from selenium.webdriver.support.ui import *

driver = webdriver.Chrome()
driver.set_window_position(-1200, 0)
driver.maximize_window()
driver.get("http://www.amazon.com/");
# driver.implicitly_wait(20)
WebDriverWait(driver, 20).until(EC.presence_of_element_located((By.ID, 'twotabsearchtextbox')))
search = driver.find_element(By.ID, 'twotabsearchtextbox')
search.click()
search.send_keys('Laptop hp core i5')

第二个问题是我有时看到WebDriverWait方法赋值给一个变量，我的意思是这样的：

element = WebDriverWait(driver, 20).until(EC.presence_of_element_located((By.ID, 'twotabsearchtextbox'))))

有什么区别？

我以为 WebDriverWait 只是等待项目出现 和 driver.implicitly_wait(20) 函数 等待页面加载。

至于我是怎么回事，两种方法都在等待页面加载

Answer 1

隐式等待

通过 , the WebDriver instance polls the HTML DOM 尝试查找任何元素时持续一定时间。当网页上的某些元素不能立即使用并且需要一些时间加载时，这很有用。默认情况下，隐式等待元素出现是禁用的，需要在 per-session 的基础上手动启用。例如：

driver.implicitly_wait(10)

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显式等待

allows our code to halt program execution, or freeze the thread, until the condition we pass it resolves. The condition is called with a certain frequency until the timeout of the wait is elapsed. This means that for as long as the condition returns a falsy value, it will keep trying and waiting. Thus Explicit waits allows us to wait for a condition to occur which inturn synchronises the state between the browser and its DOM Tree，以及 WebDriver 脚本。例如：

element = WebDriverWait(driver, 20).until(EC.presence_of_element_located((By.ID, 'twotabsearchtextbox')))

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注意事项

不要混用隐式和显式等待。这样做会导致不可预测的等待时间。例如，设置 10 秒的隐式等待和 15[=36 秒的显式等待=] 秒可能导致在 20 秒后发生超时。