python - 使用for循环时如何跳过列表中的项目

Question

我试图跳过列表中的此项，因为它会创建一个异常。我使用了 try 和 except 以及 if 语句，但它仍然无法正常工作，而是忽略了我的 if 语句。如果我将 if 语句放在异常中，则无法使用 continue，因为 continue 仅在循环中有效。有办法吗？

import time
from selenium import webdriver
import selenium
from selenium.webdriver.chrome import service
from selenium.webdriver.chrome.service import Service
from selenium.webdriver.common.keys import Keys
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC
import pandas as pd

#class scraperdata():

ser= Service("C:\Program Files (x86)\chromedriver.exe")
options = webdriver.ChromeOptions()
options.add_experimental_option('excludeSwitches', ['enable-logging'])
driver = webdriver.Chrome(options=options,service=ser)
driver.get('https://soundcloud.com/jujubucks')
print(driver.title)

wait = WebDriverWait(driver,30)

wait.until(EC.element_to_be_clickable((By.ID,"onetrust-accept-btn-handler"))).click()

try:
    i = 1
    for _ in range(32):
        song_contents = driver.find_element(By.XPATH, "//li[@class='soundList__item'][{}]".format(i))
        driver.execute_script("arguments[0].scrollIntoView(true);",song_contents)
        search = song_contents.find_element(By.XPATH, ".//a[contains(@class,'soundTitle__username')]/span").text
        search_song = song_contents.find_element(By.XPATH, ".//a[contains(@class,'soundTitle__title')]/span").text
        search_date = song_contents.find_element(By.XPATH, ".//time[contains(@class,'relativeTime')]/span").text
        search_plays = song_contents.find_element(By.XPATH, ".//span[contains(@class,'sc-ministats-small')]/span").text
        i+=1
        if search_plays == False:
            continue
        
        option ={
        'Artist': search, 
        'Song_title': search_song, 
        'Date': search_date,
        'Streams': search_plays
        }
        song_list = []
        song_list.append(option)

        df = pd.DataFrame(song_list)
        print(df)
except Exception:
    pass
driver.quit()

例外

Traceback (most recent call last):
  File "C:\Program Files\WindowsApps\PythonSoftwareFoundation.Python.3.9_3.9.2032.0_x64__qbz5n2kfra8p0\lib\runpy.py", line 197, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "C:\Program Files\WindowsApps\PythonSoftwareFoundation.Python.3.9_3.9.2032.0_x64__qbz5n2kfra8p0\lib\runpy.py", line 87, in _run_code 
    exec(code, run_globals)
  File "c:\Users\houst\.vscode\extensions\ms-python.python-2021.10.1365161279\pythonFiles\lib\python\debugpy\__main__.py", line 45, in <module>
    cli.main()
  File "c:\Users\houst\.vscode\extensions\ms-python.python-2021.10.1365161279\pythonFiles\lib\python\debugpy/..\debugpy\server\cli.py", line 444, in main
    run()
  File "c:\Users\houst\.vscode\extensions\ms-python.python-2021.10.1365161279\pythonFiles\lib\python\debugpy/..\debugpy\server\cli.py", line 285, in run_file
    runpy.run_path(target_as_str, run_name=compat.force_str("__main__"))
  File "C:\Program Files\WindowsApps\PythonSoftwareFoundation.Python.3.9_3.9.2032.0_x64__qbz5n2kfra8p0\lib\runpy.py", line 268, in run_path 
    return _run_module_code(code, init_globals, run_name,
  File "C:\Program Files\WindowsApps\PythonSoftwareFoundation.Python.3.9_3.9.2032.0_x64__qbz5n2kfra8p0\lib\runpy.py", line 97, in _run_module_code
    _run_code(code, mod_globals, init_globals,
  File "C:\Program Files\WindowsApps\PythonSoftwareFoundation.Python.3.9_3.9.2032.0_x64__qbz5n2kfra8p0\lib\runpy.py", line 87, in _run_code 
    exec(code, run_globals)
  File "c:\Users\houst\API\Scraper.py", line 34, in <module>
    search_plays = song_contents.find_element(By.XPATH, ".//span[contains(@class,'sc-ministats-small')]/span").text
  File "C:\Users\houst\Envs\Mach\lib\site-packages\selenium\webdriver\remote\webelement.py", line 718, in find_element
    return self._execute(Command.FIND_CHILD_ELEMENT,
  File "C:\Users\houst\Envs\Mach\lib\site-packages\selenium\webdriver\remote\webelement.py", line 693, in _execute
    return self._parent.execute(command, params)
  File "C:\Users\houst\Envs\Mach\lib\site-packages\selenium\webdriver\remote\webdriver.py", line 418, in execute
    self.error_handler.check_response(response)
  File "C:\Users\houst\Envs\Mach\lib\site-packages\selenium\webdriver\remote\errorhandler.py", line 243, in check_response
    raise exception_class(message, screen, stacktrace)
selenium.common.exceptions.NoSuchElementException: Message: no such element: Unable to locate element: {"method":"xpath","selector":".//span[contains(@class,'sc-ministats-small')]/span"}

标签： pythonseleniumfor-loopselenium-webdriver

Answer 1

try except最好只包装在块中引发异常的最少行。

在您的回溯中：

File "c:\Users\houst\API\Scraper.py", line 34, in <module>
    search_plays = song_contents.find_element(By.XPATH, ".//span[contains(@class,'sc-ministats-small')]/span").text

您可以看到引发异常的确切行和编号。

稍后的：

selenium.common.exceptions.NoSuchElementException: Message: no such element: Unable to locate element: {"method":"xpath","selector":".//span[contains(@class,'sc-ministats-small')]/span"}

您会看到正在引发的确切异常。

for循环具有用于继续下一次迭代的内置机制。continue声明。

使用这些知识，您可以将有问题的行包含在try/中except，并仅捕获您关心的异常。您还需要先导入该异常。

from selenium.common.exceptions import NoSuchElementException
try:
    search_plays = song_contents.find_element(By.XPATH, ".//span[contains(@class,'sc-ministats-small')]/span").text
except NoSuchElementException:
    continue

您还可以修改for循环以从1using32进行迭代range(1, 33)。这样你就不需要手动增加i.

完整代码：

import time
from selenium import webdriver
import selenium
from selenium.webdriver.chrome import service
from selenium.webdriver.chrome.service import Service
from selenium.webdriver.common.keys import Keys
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.common.exceptions import NoSuchElementException
import pandas as pd

#class scraperdata():

ser = Service("C:\Program Files (x86)\chromedriver.exe")
options = webdriver.ChromeOptions()
options.add_experimental_option('excludeSwitches', ['enable-logging'])
driver = webdriver.Chrome(options=options,service=ser)
driver.get('https://soundcloud.com/jujubucks')
print(driver.title)

wait = WebDriverWait(driver,30)

wait.until(EC.element_to_be_clickable((By.ID,"onetrust-accept-btn-handler"))).click()

for i in range(1, 33):
    song_contents = driver.find_element(By.XPATH, "//li[@class='soundList__item'][{}]".format(i))
    driver.execute_script("arguments[0].scrollIntoView(true);",song_contents)
    try:    
        search = song_contents.find_element(By.XPATH, ".//a[contains(@class,'soundTitle__username')]/span").text
        search_song = song_contents.find_element(By.XPATH, ".//a[contains(@class,'soundTitle__title')]/span").text
        search_date = song_contents.find_element(By.XPATH, ".//time[contains(@class,'relativeTime')]/span").text
        search_plays = song_contents.find_element(By.XPATH, ".//span[contains(@class,'sc-ministats-small')]/span").text
    except NoSuchElementException:
        continue
    if search_plays == False:
        continue
    
    option ={
        'Artist': search, 
        'Song_title': search_song, 
        'Date': search_date,
        'Streams': search_plays
    }
    song_list = []
    song_list.append(option)

    df = pd.DataFrame(song_list)
    print(df)
driver.quit()