How can I use selenium to record mathjax loading time

问题

I am trying to use selenium get asynchronous elements(MathJax equation) loading time.

I try to write a python-selenium script to record the loading time of my website, but my website contains a lot of equation which converted by Mathjax asynchronous, so that I cannot record it correctly.

I try to use "performance.timing" to record the loading time first, but it only can provide me 'load time'.

from selenium import webdriver
source = "url"
driver = webdriver.Chrome()
driver.get(source)
navigationStart = driver.execute_script("return window.performance.timing.navigationStart")
loadEventEnd = driver.execute_script("return window.performance.timing.loadEventEnd")
load_time = loadEventEnd - navigationStart

Then, I try to locate the ID of "MathJax" and wait until one mathjax element (e.g "MathJax-Element-1-Frame") is loaded

from selenium import webdriver
import time
from selenium.webdriver.support.wait import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC
from selenium.webdriver.common.by import By
source = "url"
driver = webdriver.Chrome()
begin = time.time()
driver.get(source)
locator = (By.ID, 'MathJax-Element-1-Frame')
WebDriverWait(driver, 20, 0.5).until(EC.presence_of_element_located(locator))
end = time.time()
finish_time = end - begin

But the time is not absolutely correct.

回答1:

Try using datetime.utcnow() with timedelta that is:

A duration expressing the difference between two datetime instances to microsecond resolution.

from datetime import datetime, timedelta
from selenium import webdriver
import time
from selenium.webdriver.support.wait import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC
from selenium.webdriver.common.by import By
source = "url"
driver = webdriver.Chrome()
begin = datetime.utcnow() + timedelta(1)
driver.get(source)
locator = (By.ID, 'MathJax-Element-1-Frame')
WebDriverWait(driver, 20, 0.5).until(EC.presence_of_element_located(locator))
end = datetime.utcnow() + timedelta(1)
finish_time = end - begin

Update

This is a function that waits for all pendingRequests to load. It might help in your case too.

def wait_until_loaded(driver, seconds: int = 30) -> None:
    java_script_to_load = "var injector = window.angular.element('body').injector();"\
                                  " var $http = injector.get('$http');" \
                                  "return ($http.pendingRequests.length === 0);"
    end_time = datetime.utcnow() + timedelta(seconds=seconds)
    print("wait for All Elements....")
    while datetime.utcnow() <= end_time:
        try:
            if driver.execute_script(java_script_to_load):
                print(f"loaded in"
                      f" {datetime.utcnow() + timedelta(seconds=seconds) - end_time}seconds")
                sleep(1)
                return
        except WebDriverException:
            continue
        sleep(0.1)
    raise TimeoutError("waiting for elements for too long")

Hope this helps you!

来源：https://stackoverflow.com/questions/56627965/how-can-i-use-selenium-to-record-mathjax-loading-time

标签

python

selenium

mathjax

execute-script