如何修复“消息：找不到元素：{”method“：”name“,”selector“：”username“}”

Question

browser = webdriver.Firefox()


try:

    browser.set_window_size(1080,800)

    browser.get('https://www.instagram.com/accounts/login')

    print (browser.title)

    time.sleep(5)

    # i used the screenshot to cheek the problem , but the screenshot is totally
    # blank (just a whit screen )  

    browser.save_screenshot("screenshot.png")
    print("clicked..!")
    browser.find_element_by_name("username").send_keys('*****')
    browser.find_element_by_name("password").send_keys('*****')

finally:
    browser.quit()

登录·Instagram点击..！

Traceback (most recent call last):
  File "/home/Sourabh58/bot1.py", line 25, in <module>
    browser.find_element_by_name("username").send_keys('be_fully_motivated')
  File "/usr/lib/python3.7/site-packages/selenium/webdriver/remote/webdriver.py", line 365, in find_element_by_name
    return self.find_element(by=By.NAME, value=name)
  File "/usr/lib/python3.7/site-packages/selenium/webdriver/remote/webdriver.py", line 752, in find_element
    'value': value})['value']
  File "/usr/lib/python3.7/site-packages/selenium/webdriver/remote/webdriver.py", line 236, in execute
    self.error_handler.check_response(response)
  File "/usr/lib/python3.7/site-packages/selenium/webdriver/remote/errorhandler.py", line 192, in check_response
    raise exception_class(message, screen, stacktrace)
selenium.common.exceptions.NoSuchElementException: Message: Unable to locate element: {"method":"name","selector":"username"}

Answer 1

使用time.sleep（）是某种形式的反模式，因为即使元素在DOM中出现得更快，测试也要等待5秒。

考虑重构代码以使用显式等待，这样WebDriver将轮询DOM以查找元素存在（或不存在），并在找到元素后立即继续。

建议的代码更改：

driver.get('https://www.instagram.com/accounts/login')

username = WebDriverWait(driver, 10).until(expected_conditions.presence_of_element_located((By.NAME, 'username')))
username.send_keys("****")
password = WebDriverWait(driver, 10).until(expected_conditions.presence_of_element_located((By.NAME, 'password')))
password.send_keys("****")