Python脚本，它使用，尝试(失败)打印列表框中包含的元素

Question

我正在运行的脚本如下：

    #import necessary packages
    from selenium import webdriver


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

    #run on headless browser
    chrome_options = Options()
    chrome_options.add_argument("--headless")
    driver = webdriver.Chrome(options=chrome_options)
    ####

    #driver = webdriver.Chrome()
    # Open the website
    driver.get('https://euclid.eba.europa.eu/register/pir/search')
    driver.set_window_size(1200, 800)
    driver.maximize_window()

    #find element using the link text
    xpath_institution_search = "//a[@href='/register/pir/search' and contains(text(), 'InstitutionSearch')]"                        
    try:
        element = WebDriverWait(driver, 10).until(
            EC.presence_of_element_located((By.XPATH, xpath_institution_search))
)
    finally: 
        institution_search = driver.find_element_by_xpath(xpath_institution_search)
        driver.execute_script("return arguments[0].scrollIntoView();", institution_search)
        institution_search.click()

    #select all appropriate National Competent Authorities
    xpath_nca_list_new = '(//p-listbox[@class="col-md-9 ng-untouched ng-pristine ng-valid" and @name="ncaList"])'                   
    #find the listbox element using it's xpath
    nca_listbox = driver.find_element_by_xpath(xpath_nca_list_new)
    #find elements within list box using tag names
    nca_div_tags = nca_listbox.find_elements_by_tag_name("div")
    #find element representing "select all" checkbox
    select_all_ncas = nca_div_tags[5]
    #find all list content (National Competent Authorities)
    nca_content_list = nca_div_tags[0].find_elements_by_tag_name("ul")
    #store list content in an ordered list 
    ncas = nca_content_list[0].find_elements_by_tag_name("li")

    #make web driver wait until element is visible before further action
    try:
        element = WebDriverWait(driver, 10).until(
        EC.presence_of_element_located((By.XPATH, xpath_nca_list_new)))
    finally:
        count = 1
        #print out list of ncas
        for item in ncas:
            text = item.text
            print(str(count) + ". " + text)
            count=count+1

我对Python非常陌生，所以请原谅任何糟糕的代码。代码有时会打印如下所示的所有listbox元素的列表：

1. AT -奥地利金融市场管理局
2. -比利时国家银行-保加利亚国家银行
3. CY-塞浦路斯中央银行H 110CZ-捷克国家银行H 211H 112DE-联邦金融监督局<
4. >H 213<代码>H 114>DK-丹麦金融监督局H 215H116EE-爱沙尼亚金融监督局H 217/code>H118/code>ES- Bank of西班牙H 219/code><>H120/code>芬兰金融监管机构代码< of >< of >< of >>>>><
5. ><
6. ><
7. ><>H 211><代码>代码><代码>><代码>H120/H120>芬兰金融监管机构代码<
8. 克罗地亚国家银行--匈牙利中央银行--匈牙利中央银行-匈牙利中央银行-爱尔兰中央银行-爱尔兰中央银行-金融监督局-金融监督局-意大利银行-H 138-金融市场管理局- Liechtenstein
9. LT -立陶宛银行-H 241H 142LU-金融部门监督委员会H 243H 144LV>金融和资本市场代码Commission
10. MT -马耳他金融服务局H 247/code>H 148NL-荷兰银行H 249H 150没有--挪威金融管理局金融代码< /code>HR HR>葡萄牙银行
11. RO-罗马尼亚国家银行
12. SE-瑞典金融监督局
13. SI-斯洛文尼亚银行
14. SK-斯洛伐克国家银行

G 264

但有时返回的列表是空的。在同一个网页上还有另外两个列表框，这段代码对于这些元素来说是一致的。

有人能解释一下为什么会发生这种事吗？提前谢谢。下面是我试图使用的listbox元素的HTML代码。

<p-listbox class="col-md-9 ng-untouched ng-pristine ng-valid" name="ncaList" optionlabel="CodeDisplayValue" _ngcontent-bwu-c7="">
<div class="ui-listbox ui-inputtext ui-widget ui-widget-content ui-corner-all" style="width: 100%;">
    <div class="ui-helper-hidden-accessible">
        <input type="text" readonly="readonly">
    </div>
    <!---->
    <!---->
    <div class="ui-widget-header ui-corner-all ui-listbox-header ui-helper-clearfix ui-listbox-header-w-checkbox ng-star-inserted">
        <!---->
        <div class="ui-chkbox ui-widget ng-star-inserted">
            <div class="ui-helper-hidden-accessible">
                <input type="checkbox" readonly="readonly">
            </div>
            <div class="ui-chkbox-box ui-widget ui-corner-all ui-state-default"><span class="ui-chkbox-icon ui-clickable"></span></div>
        </div>
        <!---->
    </div>
    <div class="ui-listbox-list-wrapper" style="max-height: 250px;">
        <ul class="ui-listbox-list">
            <!---->
            <li tabindex="0" class="ui-listbox-item ui-corner-all ng-star-inserted" style="display: block;">
                <!---->
                <div class="ui-chkbox ui-widget ng-star-inserted">
                    <div class="ui-chkbox-box ui-widget ui-corner-all ui-state-default"><span class="ui-chkbox-icon ui-clickable"></span></div>
                </div>
                <!----><span class="ng-star-inserted">AT - Austrian Financial Market Authority</span>
                <!---->
            </li>
            <li tabindex="0" class="ui-listbox-item ui-corner-all ng-star-inserted" style="display: block;">
                <!---->
                <div class="ui-chkbox ui-widget ng-star-inserted">
                    <div class="ui-chkbox-box ui-widget ui-corner-all ui-state-default"><span class="ui-chkbox-icon ui-clickable"></span></div>
                </div>
                <!----><span class="ng-star-inserted">BE - National Bank of Belgium</span>
                <!---->
            </li>
            <li tabindex="0" class="ui-listbox-item ui-corner-all ng-star-inserted" style="display: block;">
                <!---->
                <div class="ui-chkbox ui-widget ng-star-inserted">
                    <div class="ui-chkbox-box ui-widget ui-corner-all ui-state-default"><span class="ui-chkbox-icon ui-clickable"></span></div>
                </div>
                <!----><span class="ng-star-inserted">BG - Bulgarian National Bank</span>
                <!---->
            </li>
            <li tabindex="0" class="ui-listbox-item ui-corner-all ng-star-inserted" style="display: block;">
                <!---->
                <div class="ui-chkbox ui-widget ng-star-inserted">
                    <div class="ui-chkbox-box ui-widget ui-corner-all ui-state-default"><span class="ui-chkbox-icon ui-clickable"></span></div>
                </div>
                <!----><span class="ng-star-inserted">CY - Central Bank of Cyprus</span>
                <!---->
            </li>
            <li tabindex="0" class="ui-listbox-item ui-corner-all ng-star-inserted" style="display: block;">
                <!---->
                <div class="ui-chkbox ui-widget ng-star-inserted">
                    <div class="ui-chkbox-box ui-widget ui-corner-all ui-state-default"><span class="ui-chkbox-icon ui-clickable"></span></div>
                </div>
                <!----><span class="ng-star-inserted">CZ - Czech National Bank</span>
                <!---->
            </li>
            <li tabindex="0" class="ui-listbox-item ui-corner-all ng-star-inserted" style="display: block;">
                <!---->
                <div class="ui-chkbox ui-widget ng-star-inserted">
                    <div class="ui-chkbox-box ui-widget ui-corner-all ui-state-default"><span class="ui-chkbox-icon ui-clickable"></span></div>
                </div>
                <!----><span class="ng-star-inserted">DE - Federal Financial Supervisory Authority</span>
                <!---->
            </li>
            <li tabindex="0" class="ui-listbox-item ui-corner-all ng-star-inserted" style="display: block;">
                <!---->
                <div class="ui-chkbox ui-widget ng-star-inserted">
                    <div class="ui-chkbox-box ui-widget ui-corner-all ui-state-default"><span class="ui-chkbox-icon ui-clickable"></span></div>
                </div>
                <!----><span class="ng-star-inserted">DK - Danish Financial Supervisory Authority</span>
                <!---->
            </li>
            <li tabindex="0" class="ui-listbox-item ui-corner-all ng-star-inserted" style="display: block;">
                <!---->
                <div class="ui-chkbox ui-widget ng-star-inserted">
                    <div class="ui-chkbox-box ui-widget ui-corner-all ui-state-default"><span class="ui-chkbox-icon ui-clickable"></span></div>
                </div>
                <!----><span class="ng-star-inserted">EE - Estonian Financial Supervision Authority</span>
                <!---->
            </li>
            <li tabindex="0" class="ui-listbox-item ui-corner-all ng-star-inserted" style="display: block;">
                <!---->
                <div class="ui-chkbox ui-widget ng-star-inserted">
                    <div class="ui-chkbox-box ui-widget ui-corner-all ui-state-default"><span class="ui-chkbox-icon ui-clickable"></span></div>
                </div>
                <!----><span class="ng-star-inserted">ES - Bank of Spain</span>
                <!---->
            </li>
            <li tabindex="0" class="ui-listbox-item ui-corner-all ng-star-inserted" style="display: block;">
                <!---->
                <div class="ui-chkbox ui-widget ng-star-inserted">
                    <div class="ui-chkbox-box ui-widget ui-corner-all ui-state-default"><span class="ui-chkbox-icon ui-clickable"></span></div>
                </div>
                <!----><span class="ng-star-inserted">FI - Finnish Financial Supervisory Authority</span>
                <!---->
            </li>
            <li tabindex="0" class="ui-listbox-item ui-corner-all ng-star-inserted" style="display: block;">
                <!---->
                <div class="ui-chkbox ui-widget ng-star-inserted">
                    <div class="ui-chkbox-box ui-widget ui-corner-all ui-state-default"><span class="ui-chkbox-icon ui-clickable"></span></div>
                </div>
                <!----><span class="ng-star-inserted">FR - Prudential Supervisory and Resolution Authority</span>
                <!---->
            </li>
            <li tabindex="0" class="ui-listbox-item ui-corner-all ng-star-inserted" style="display: block;">
                <!---->
                <div class="ui-chkbox ui-widget ng-star-inserted">
                    <div class="ui-chkbox-box ui-widget ui-corner-all ui-state-default"><span class="ui-chkbox-icon ui-clickable"></span></div>
                </div>
                <!----><span class="ng-star-inserted">GB - Financial Conduct Authority (FCA)</span>
                <!---->
            </li>
            <li tabindex="0" class="ui-listbox-item ui-corner-all ng-star-inserted" style="display: block;">
                <!---->
                <div class="ui-chkbox ui-widget ng-star-inserted">
                    <div class="ui-chkbox-box ui-widget ui-corner-all ui-state-default"><span class="ui-chkbox-icon ui-clickable"></span></div>
                </div>
                <!----><span class="ng-star-inserted">GR - Bank of Greece</span>
                <!---->
            </li>
            <li tabindex="0" class="ui-listbox-item ui-corner-all ng-star-inserted" style="display: block;">
                <!---->
                <div class="ui-chkbox ui-widget ng-star-inserted">
                    <div class="ui-chkbox-box ui-widget ui-corner-all ui-state-default"><span class="ui-chkbox-icon ui-clickable"></span></div>
                </div>
                <!----><span class="ng-star-inserted">HR - Croatian National Bank</span>
                <!---->
            </li>
            <li tabindex="0" class="ui-listbox-item ui-corner-all ng-star-inserted" style="display: block;">
                <!---->
                <div class="ui-chkbox ui-widget ng-star-inserted">
                    <div class="ui-chkbox-box ui-widget ui-corner-all ui-state-default"><span class="ui-chkbox-icon ui-clickable"></span></div>
                </div>
                <!----><span class="ng-star-inserted">HU - Central Bank of Hungary</span>
                <!---->
            </li>
            <li tabindex="0" class="ui-listbox-item ui-corner-all ng-star-inserted" style="display: block;">
                <!---->
                <div class="ui-chkbox ui-widget ng-star-inserted">
                    <div class="ui-chkbox-box ui-widget ui-corner-all ui-state-default"><span class="ui-chkbox-icon ui-clickable"></span></div>
                </div>
                <!----><span class="ng-star-inserted">IE - Central Bank of Ireland</span>
                <!---->
            </li>
            <li tabindex="0" class="ui-listbox-item ui-corner-all ng-star-inserted" style="display: block;">
                <!---->
                <div class="ui-chkbox ui-widget ng-star-inserted">
                    <div class="ui-chkbox-box ui-widget ui-corner-all ui-state-default"><span class="ui-chkbox-icon ui-clickable"></span></div>
                </div>
                <!----><span class="ng-star-inserted">IS - Financial Supervisory Authority</span>
                <!---->
            </li>
            <li tabindex="0" class="ui-listbox-item ui-corner-all ng-star-inserted" style="display: block;">
                <!---->
                <div class="ui-chkbox ui-widget ng-star-inserted">
                    <div class="ui-chkbox-box ui-widget ui-corner-all ui-state-default"><span class="ui-chkbox-icon ui-clickable"></span></div>
                </div>
                <!----><span class="ng-star-inserted">IT - Bank of Italy</span>
                <!---->
            </li>
            <li tabindex="0" class="ui-listbox-item ui-corner-all ng-star-inserted" style="display: block;">
                <!---->
                <div class="ui-chkbox ui-widget ng-star-inserted">
                    <div class="ui-chkbox-box ui-widget ui-corner-all ui-state-default"><span class="ui-chkbox-icon ui-clickable"></span></div>
                </div>
                <!----><span class="ng-star-inserted">LI - Financial Market Authority Liechtenstein</span>
                <!---->
            </li>
            <li tabindex="0" class="ui-listbox-item ui-corner-all ng-star-inserted" style="display: block;">
                <!---->
                <div class="ui-chkbox ui-widget ng-star-inserted">
                    <div class="ui-chkbox-box ui-widget ui-corner-all ui-state-default"><span class="ui-chkbox-icon ui-clickable"></span></div>
                </div>
                <!----><span class="ng-star-inserted">LT - Bank of Lithuania</span>
                <!---->
            </li>
            <li tabindex="0" class="ui-listbox-item ui-corner-all ng-star-inserted" style="display: block;">
                <!---->
                <div class="ui-chkbox ui-widget ng-star-inserted">
                    <div class="ui-chkbox-box ui-widget ui-corner-all ui-state-default"><span class="ui-chkbox-icon ui-clickable"></span></div>
                </div>
                <!----><span class="ng-star-inserted">LU - Commission for the Supervision of Financial Sector</span>
                <!---->
            </li>
            <li tabindex="0" class="ui-listbox-item ui-corner-all ng-star-inserted" style="display: block;">
                <!---->
                <div class="ui-chkbox ui-widget ng-star-inserted">
                    <div class="ui-chkbox-box ui-widget ui-corner-all ui-state-default"><span class="ui-chkbox-icon ui-clickable"></span></div>
                </div>
                <!----><span class="ng-star-inserted">LV - Financial and Capital Market Commission</span>
                <!---->
            </li>
            <li tabindex="0" class="ui-listbox-item ui-corner-all ng-star-inserted" style="display: block;">
                <!---->
                <div class="ui-chkbox ui-widget ng-star-inserted">
                    <div class="ui-chkbox-box ui-widget ui-corner-all ui-state-default"><span class="ui-chkbox-icon ui-clickable"></span></div>
                </div>
                <!----><span class="ng-star-inserted">MT - Malta Financial Services Authority</span>
                <!---->
            </li>
            <li tabindex="0" class="ui-listbox-item ui-corner-all ng-star-inserted" style="display: block;">
                <!---->
                <div class="ui-chkbox ui-widget ng-star-inserted">
                    <div class="ui-chkbox-box ui-widget ui-corner-all ui-state-default"><span class="ui-chkbox-icon ui-clickable"></span></div>
                </div>
                <!----><span class="ng-star-inserted">NL - The Netherlands Bank</span>
                <!---->
            </li>
            <li tabindex="0" class="ui-listbox-item ui-corner-all ng-star-inserted" style="display: block;">
                <!---->
                <div class="ui-chkbox ui-widget ng-star-inserted">
                    <div class="ui-chkbox-box ui-widget ui-corner-all ui-state-default"><span class="ui-chkbox-icon ui-clickable"></span></div>
                </div>
                <!----><span class="ng-star-inserted">NO - The Financial Authority of Norway</span>
                <!---->
            </li>
            <li tabindex="0" class="ui-listbox-item ui-corner-all ng-star-inserted" style="display: block;">
                <!---->
                <div class="ui-chkbox ui-widget ng-star-inserted">
                    <div class="ui-chkbox-box ui-widget ui-corner-all ui-state-default"><span class="ui-chkbox-icon ui-clickable"></span></div>
                </div>
                <!----><span class="ng-star-inserted">PL - Polish Financial Supervision Authority</span>
                <!---->
            </li>
            <li tabindex="0" class="ui-listbox-item ui-corner-all ng-star-inserted" style="display: block;">
                <!---->
                <div class="ui-chkbox ui-widget ng-star-inserted">
                    <div class="ui-chkbox-box ui-widget ui-corner-all ui-state-default"><span class="ui-chkbox-icon ui-clickable"></span></div>
                </div>
                <!----><span class="ng-star-inserted">PT - Bank of Portugal</span>
                <!---->
            </li>
            <li tabindex="0" class="ui-listbox-item ui-corner-all ng-star-inserted" style="display: block;">
                <!---->
                <div class="ui-chkbox ui-widget ng-star-inserted">
                    <div class="ui-chkbox-box ui-widget ui-corner-all ui-state-default"><span class="ui-chkbox-icon ui-clickable"></span></div>
                </div>
                <!----><span class="ng-star-inserted">RO - National Bank of Romania</span>
                <!---->
            </li>
            <li tabindex="0" class="ui-listbox-item ui-corner-all ng-star-inserted" style="display: block;">
                <!---->
                <div class="ui-chkbox ui-widget ng-star-inserted">
                    <div class="ui-chkbox-box ui-widget ui-corner-all ui-state-default"><span class="ui-chkbox-icon ui-clickable"></span></div>
                </div>
                <!----><span class="ng-star-inserted">SE - Swedish Financial Supervisory Authority</span>
                <!---->
            </li>
            <li tabindex="0" class="ui-listbox-item ui-corner-all ng-star-inserted" style="display: block;">
                <!---->
                <div class="ui-chkbox ui-widget ng-star-inserted">
                    <div class="ui-chkbox-box ui-widget ui-corner-all ui-state-default"><span class="ui-chkbox-icon ui-clickable"></span></div>
                </div>
                <!----><span class="ng-star-inserted">SI - Bank of Slovenia</span>
                <!---->
            </li>
            <li tabindex="0" class="ui-listbox-item ui-corner-all ng-star-inserted" style="display: block;">
                <!---->
                <div class="ui-chkbox ui-widget ng-star-inserted">
                    <div class="ui-chkbox-box ui-widget ui-corner-all ui-state-default"><span class="ui-chkbox-icon ui-clickable"></span></div>
                </div>
                <!----><span class="ng-star-inserted">SK - National Bank of Slovakia</span>
                <!---->
            </li>
        </ul>
    </div>
    <!---->
</div>

​

Answer 1

改进的定位器和等待到liist的visibility_of_all_elements_located：

wait = WebDriverWait(driver, 10)
wait.until(EC.element_to_be_clickable((By.LINK_TEXT, "Institution Search"))).click()
search_button = wait.until(EC.element_to_be_clickable((By.CSS_SELECTOR, "[label=Search] button")))
driver.execute_script("arguments[0].scrollIntoView()", search_button)
search_button.click()

nca_list = wait.until(EC.visibility_of_all_elements_located((By.CSS_SELECTOR, "[name=ncaList] li")))
for nca in nca_list:
    print(nca.text)