Detailed explanation of three methods of selenium setting element waiting

Selenium There are three ways to set element waiting

1. sleep  Mandatory waiting 
2. implicitly_wait()  The recessive waiting 
3. WebDriverWait()  According to wait 

The advantages and disadvantages of the three methods

sleep Mandatory waiting

from selenium import webdriver
from time import sleep
driver = webdriver.Chrome()
sleep(2)        # Set the wait 2 Second 
driver.get('http://www.baidu.com')

• advantage ： Code Introduction , Simple and clear
• shortcoming ： If you set sleep The waiting time is too short , The element hasn't been loaded yet , Application error ,sleep Set the waiting time too long , The element has already been loaded , The program is still waiting , Waste is time , Affect the overall efficiency of the code
• Personal view ： Simple and crude , Set a reasonable sleep time according to the response speed of the website and your own network speed

implicitly_wait() The recessive waiting

from selenium import webdriver
from time import sleep
driver = webdriver.Chrome()
driver.implicitly_wait(20)  # Set the wait 20 Second 
driver.get('http://www.baidu.com')

• advantage ：

1. Code Introduction
2. Add implicitly_wait(10) , The whole process will be effective （ Act on the whole , I'm just going to initialize it driver Add... After , The following code will be affected ）, Will wait for the element to be loaded
3. The whole page is not loaded within the set time , Will report NosuchElementError. If the element is in the 10s Be loaded out , Automatically execute the following script , Not always waiting for 10s

• shortcoming ：

1. You have to load the entire page to execute the code , This affects the efficiency of code execution , In general , The result we want is to execute the code just by loading the element I want to locate , There is no need to wait for the entire page to be fully loaded before executing the code .

• Personal view ：

1. Not suitable for data in ajax Web site , Like turning the page or something , An element always exists , But the data keeps changing , In this case, just load the first page , The data on the next page will be the same as the data on the first page , Because the code judges that this element has been loaded , Won't wait ajax To load the

WebDriverWait（） According to wait

from selenium import webdriver
from selenium.webdriver.support import expected_conditions as EC
from selenium.webdriver.support.ui import WebDriverWait       #WebDriverWait Pay attention to case 
from selenium.webdriver.common.by import By
driver = webdriver.Chrome()
driver.get('http://www.baidu.com')
try:
    element = 
    WebDriverWait(driver,10).until(EC.presence_of_element_located((By.ID,'kw')))
    element.send_keys('123')
    driver.find_element_by_id('su').click()
except Exception as message:
   print(' Element positioning error %s'%message)
finally:
   pass

• advantage ：

Fast code execution . Don't wait for the entire page to load , Just load the element you want to locate and execute the code . It is the most intelligent way to set element waiting .

• shortcoming ：

1. To import
from selenium.webdriver.support import expected_conditions as EC
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.common.by import By
You must import the above 3 A package , The guided package path is quite complex , Wordy and troublesome
2. Writing waiting time code is also complex . There are a little more steps .
element=WebDriverWait(driver,10).until(EC.presence_of_element_located((By.ID,‘kw’)))
element.send_keys(‘123’)

• Personal view ：

Compared to two , This way can be considered as a good , But it's just trouble , Write too much code , It can be used in the first way sleep A mixture of , But I still like to use sleep, Self use selenium Just can't break the website , Or use selenium It is better than direct cracking to use this , Personally, I don't need it if I can , Grabbing speed is too slow .

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Link to the original text ：https://blog.csdn.net/Gscsd_T/article/details/102837046