定位元素顯式等待和不等待有什么區別？-有解無憂

問題是關于 selenium webdriver 的顯式等待功能，它與超時的定位操作相同。Webdriver 等待元素可見或存在。在我的情況下，我定位具有顯式等待和沒有它的元素。當它沒有顯式等待時，它會找到并分配它。但在下面，我也嘗試找到顯式等待的元素，該變數未分配，并以這種形式傳遞給 for 迭代，我的 for 迭代讓UnboundLocalError 我知道錯誤不是 selenium 而是基于 python 的。我可以通過使用而不是passy_priceNewProds = x_priceNewProds` 來消除該錯誤，但我需要了解為什么 selenium webdriver 無法通過等待找到元素，如果它已經在上面的一行找到了它。也必須有餅干。

代碼如下；

import pandas as pd
from selenium.webdriver.chrome.service import Service
from selenium.webdriver.chrome.options import Options
from selenium import webdriver
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC
from selenium.webdriver.common.by import By

#reading from csv file url-s
def readCSV(path_csv):
    df=pd.read_csv(path_csv)
    return df

fileCSV=readCSV(r'C:\Users\Admin\Downloads\urls.csv')
length_of_column_urls=fileCSV['linkamazon'].last_valid_index()

def create_driver():
    chrome_options = Options()
    chrome_options.headless = True
    chrome_options.add_argument("start-maximized")
    # options.add_experimental_option("detach", True)
    chrome_options.add_argument("--no-sandbox")
    chrome_options.add_experimental_option("excludeSwitches", ["enable-automation"])
    chrome_options.add_experimental_option('excludeSwitches', ['enable-logging'])
    chrome_options.add_experimental_option('useAutomationExtension', False)
    chrome_options.add_argument('--disable-blink-features=AutomationControlled')

    webdriver_service = Service(r'C:\pythonPro\w_crawl\AmznScrpBot\chromedriver.exe')
    driver = webdriver.Chrome(service=webdriver_service, options=chrome_options)

    return driver

#going to urls 1-by-1
def goToUrl_Se(driver):
    global counter
    counter = 0
    for i in range(0, length_of_column_urls   1):
        xUrl = fileCSV.iloc[i, 1]
        print(xUrl,i)
        # going to url(amazn) via Selenium WebDriver
        driver.get(xUrl)
        parse_data()
        counter =1
    driver.quit()

#fetch-parse the data from url page
def parse_data():
    global asin, title, bookform, priceNewProd
    wait=WebDriverWait(driver,timeout=20)

    try:
        #trying code snippets where locating elements occur by XPATH, in some ofthem
        #there is also WebDriver explicit wait, that element has both methods
        #with presence_of element wait method and without explicit wait method. Just trying to understand
        #why sometimes elements cannot be located on page
        y_data_index=wait.until(EC.presence_of_element_located((By.XPATH,"//div[@data-index='1']")))
        print(y_data_index.text,'y_index')
        x_data_index=wait.until(EC.visibility_of_element_located((By.XPATH,"//div[@data-index='1']")))
        print(x_data_index.text,'x_index')
        x_titles=driver.find_elements(By.XPATH,'//span[contains(@class,"a-size-medium")]')
        x_bookforms = driver.find_elements(By.XPATH,'//div[contains(@class,"a-section a-spacing-none a-spacing-top-micro s-price-instructions-style")]//div[contains(@class,"a-row a-size-base a-color-base")]//a[contains(@class,"a-size-base a-link-normal puis-medium-weight-text s-underline-text s-underline-link-text s-link-style s-link-centralized-style a-text-bold")]')
        x_priceNewProds = driver.find_elements(By.XPATH,'//div[contains(@class,"a-row a-size-base a-color-base")]//span[contains(@data-a-color,"base")]//span[contains(@class,"a-offscreen")][1]')
        y_priceNewProds=wait.until(EC.visibility_of_all_elements_located((By.XPATH,'//div[contains(@class,"a-row a-size-base a-color-base")]//span[contains(@data-a-color,"base")]//span[contains(@class,"a-offscreen")][1]')))
    except:
        pass

    for i in range(len(x_titles)):
        x_title=x_titles[i].text
        x_priceNewProd = x_priceNewProds[i].text
        print(x_priceNewProd)
        y_priceNewProd=y_priceNewProds[i].text
        print(y_priceNewProd)
        try:
            x_bookform=x_bookforms[i].text
            print(x_bookform)
        except:
            x_bookform='-'
        title = x_title
        bookform = x_bookform
        priceNewProd = x_priceNewProd
        write_to_csv()

def write_to_csv():
    if counter==0:
        df=pd.DataFrame({'Products':title,'Bookform':bookform,'Price':priceNewProd},index=[0])
        wr=df.to_csv('results_new00.csv',index=False,mode='w')
    else:
        df=pd.DataFrame({'Products':title,'Bookform':bookform,'Price':priceNewProd},index=[0])
        wr=df.to_csv('results_new00.csv',index=False,mode='a',header=False)

driver=create_driver()
goToUrl_Se(driver)

y_priceNewProd=y_priceNewProds[i].text UnboundLocalError: local variable 'y_priceNewProds' referenced before assignment

uj5u.com熱心網友回復：

由于您沒有共享包括鏈接在內的所有代碼，我們無法知道那里到底發生了什么，但我猜這一行

wait.until(EC.visibility_of_all_elements_located((By.XPATH,'//div[contains(@class,"a-row a-size-base a-color-base")]//span[contains(@data-a-color,"base")]//span[contains(@class,"a-offscreen")][1]')))

拋出例外，因為該元素是 / 不可見。
這就是為什么y_priceNewProds仍然沒有分配任何值。
如果您使用簡單的driver.find_elements方法，它可以找到這些元素，因為它們存在但同樣不可見。
UPD
在您分享鏈接后，我對其進行了測驗，現在我可以說：是的，我是對的！
這些元素是不可見的。
以下代碼拋出TimeoutException

from selenium import webdriver
from selenium.webdriver.chrome.service import Service
from selenium.webdriver.chrome.options import Options
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.common.by import By
from selenium.webdriver.support import expected_conditions as EC
options = Options()
options.add_argument("start-maximized")

webdriver_service = Service('C:\webdrivers\chromedriver.exe')
driver = webdriver.Chrome(service=webdriver_service, options=options)
url = 'https://www.amazon.com/s?i=stripbooks&bbn=1&rh=n:1,p_n_feature_eighteen_browse-bin:8622846011&dc&fs=true&ds=v1:gAO0+Zc+C6RthRkqyWzOHmDVufv7JbuCK96Grvjle68&qid=1665559431&rnid=8622845011&ref=sr_nr_p_n_feature_eighteen_browse-bin_5'
driver.get(url)
wait = WebDriverWait(driver, 20)

m_list = wait.until(EC.visibility_of_all_elements_located((By.XPATH, '//div[contains(@class,"a-row a-size-base a-color-base")]//span[contains(@data-a-color,"base")]//span[contains(@class,"a-offscreen")][1]')))
print(m_list)

UPD2
但是，如果您將采用該元素的直接父元素，它將正常作業，因為它是可見的。
對于以下代碼：

from selenium import webdriver
from selenium.webdriver.chrome.service import Service
from selenium.webdriver.chrome.options import Options
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.common.by import By
from selenium.webdriver.support import expected_conditions as EC
options = Options()
options.add_argument("start-maximized")

webdriver_service = Service('C:\webdrivers\chromedriver.exe')
driver = webdriver.Chrome(service=webdriver_service, options=options)
url = 'https://www.amazon.com/s?i=stripbooks&bbn=1&rh=n:1,p_n_feature_eighteen_browse-bin:8622846011&dc&fs=true&ds=v1:gAO0+Zc+C6RthRkqyWzOHmDVufv7JbuCK96Grvjle68&qid=1665559431&rnid=8622845011&ref=sr_nr_p_n_feature_eighteen_browse-bin_5'
driver.get(url)
wait = WebDriverWait(driver, 20)

m_list = wait.until(EC.visibility_of_all_elements_located((By.XPATH, '//div[contains(@class,"a-row a-size-base a-color-base")]//span[contains(@data-a-color,"base")]')))
print(len(m_list))

輸出是：

轉載請註明出處，本文鏈接：https://www.uj5u.com/shujuku/523526.html

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