我正在尝试使用一个函数来获取在后台运行的新下载文件的名称，同时我运行另一个程序来下载特定文件。后台函数将有一个新下载文件的返回值，我打算稍后在代码中使用它。我有下面要尝试做的粗略框架。
with concurrent.futures.ThreadPoolExecutor(max_workers = 1) as executor:
output = executor.submit(downloadedfiledetector, filedirectory)
filename = output.result()
#Run code that will download a file
print(filename)
在这里，downloadedfiledetector 是返回下载文件目录的函数，filedirectory 是该函数的参数，其中包含该函数将监视的文件路径。我希望将返回值存储在文件名变量中，以便稍后在程序中使用它。然后在下面，我运行更多的代码，基本上从一个网站下载一个文件，该文件的名称每次都会不同（因此需要一个函数来获取新下载文件的名称）。
当我运行上面的代码时，它根本不运行下载文件的代码，只运行downloadedfiledetector函数。任何帮助表示赞赏！
编辑： 我被要求包括一个代码的工作示例。我知道这肯定不是最好的方法，但我自己写的（大部分）而且我对 Python 还是很陌生。在代码的底部，combinessubtitletovideo 函数是我将使用下载的 .srt 文件并将其与视频组合的地方：
import os
import time
from selenium.webdriver.common.by import By
import undetected_chromedriver as bypass
import concurrent.futures
def downloadedfiledetector(scannedfolder, variablefunction):
seconds = 0
dl_wait = True
filelist1 = []
filelist2 = []
while dl_wait and seconds < 120:
for fname in os.listdir(scannedfolder):
filelist1.append(fname)
if fname.endswith('.crdownload') and seconds != 0:
filelist1.pop()
time.sleep(1)
for fname in os.listdir(scannedfolder):
filelist2.append(fname)
if fname.endswith('.crdownload') and seconds != 0:
filelist2.pop()
if seconds != 0 and len(filelist1) != len(filelist2):
dl_wait = False
seconds += 1
if variablefunction == 1:
newfilename1 = list(set(filelist2) - set(filelist1))
newfilename2 = ''.join(str(e) for e in newfilename1)
time.sleep(1)
driver.close()
return newfilename2
elif variablefunction == 2:
pass
with concurrent.futures.ThreadPoolExecutor(max_workers = 1) as executor:
output = executor.submit(downloadedfiledetector, cliplocation, 1)
filenamesubtitle = output.result()
driver = bypass.Chrome(options=options)
driver.get(subtitleurl)
WebDriverWait(driver, 300).until(EC.element_to_be_clickable((By.CSS_SELECTOR, '#root > section > section.container.mx-auto.py-6.mt-4.sm\:mt-6 > div.mx-auto.max-w-4xl.leading-normal.mt-6.sm\:mt-10.sm\:flex.justify-center.px-4.lg\:px-0.text-center > div > div > div > input')))
enterurlbox = driver.find_element(By.CSS_SELECTOR, '#root > section > section.container.mx-auto.py-6.mt-4.sm\:mt-6 > div.mx-auto.max-w-4xl.leading-normal.mt-6.sm\:mt-10.sm\:flex.justify-center.px-4.lg\:px-0.text-center > div > div > div > input')
enterurlbox.send_keys(youtubeurl)
WebDriverWait(driver, 300).until(EC.element_to_be_clickable((By.CSS_SELECTOR, '#root > section > section.container.mx-auto.py-6.mt-4.sm\:mt-6 > div.mx-auto.max-w-4xl.leading-normal.mt-6.sm\:mt-10.sm\:flex.justify-center.px-4.lg\:px-0.text-center > button')))
downloadbutton = driver.find_element(By.CSS_SELECTOR, '#root > section > section.container.mx-auto.py-6.mt-4.sm\:mt-6 > div.mx-auto.max-w-4xl.leading-normal.mt-6.sm\:mt-10.sm\:flex.justify-center.px-4.lg\:px-0.text-center > button')
downloadbutton.click()
WebDriverWait(driver, 300).until(EC.element_to_be_clickable((By.CSS_SELECTOR, '#root > section > main > section.max-w-3xl.mx-auto.md\:flex.md\:justify-between.pt-4 > div.w-full.px-4.lg\:px-0.mb-6.md\:mb-0 > ul > li.py-6.text-center.block.w-full.px-2.sm\:px-4.sm\:py-3.sm\:flex.justify-between.items-center.border-b.border-gray-200.dark\:border-night-500 > section > div > div > a:nth-child(1)')))
srtdownloadbutton = driver.find_element(By.CSS_SELECTOR, '#root > section > main > section.max-w-3xl.mx-auto.md\:flex.md\:justify-between.pt-4 > div.w-full.px-4.lg\:px-0.mb-6.md\:mb-0 > ul > li.py-6.text-center.block.w-full.px-2.sm\:px-4.sm\:py-3.sm\:flex.justify-between.items-center.border-b.border-gray-200.dark\:border-night-500 > section > div > div > a:nth-child(1)')
srtdownloadbutton.click()
time.sleep(2)
combinesubtitletovideo(filenamesubtitle)
您可以使用从目标函数返回结果的地图功能：
with concurrent.futures.ThreadPoolExecutor(max_workers = 1) as executor:
for result in executor.map(downloadedfiledetector, filedirectory):
print(result) #this gives you the required return value from function
尝试这样的事情：
import os
import time
from selenium.webdriver.common.by import By
import undetected_chromedriver as bypass
import concurrent.futures
def downloadedfiledetector(scannedfolder, variablefunction):
pass # Code exactly like your example, omitted for clarity
def subsequent():
driver = bypass.Chrome(options=options)
# Your same code...
srtdownloadbutton.click()
# Remove time.sleep() at the end, it does nothing
with concurrent.futures.ThreadPoolExecutor(max_workers = 1) as executor:
output1 = executor.submit(downloadedfiledetector, cliplocation, 1)
output2 = executor.submit(subsequent)
filenamesubtitle = output1.result()
output2.result()
combinesubtitletovideo(filenamesubtitle)
这将在两个不同的线程中并行执行两个函数。主线程等待他们两个；他们完成的顺序无关紧要。一旦两个线程都完成（返回结果）主线程继续。
如果有人遇到过这个或有类似的问题，我解决了我自己的问题。当然，我没有花几个月的时间来解决，但我想我会在这里分享我的过程，以防其他人发现它有用。
我不应该使用并发期货库，我应该使用线程库。通过这种方式，代码实际上变得更加简单易懂：
import threading, os, time
output_file = [] #We innitialize this variable as a list. This will contain the output for the threaded function, as there is not an easy way (to my knowledge at least) to get the return value of a function. Thus, by appending the output of the threaded function to this list, we can access that output outside of the threaded function.
def downloaded_file_detector(scanned_folder, variable_function):
#input code for detecting the downloaded file. The psuedocode is as follows:
global output_file #This part may or may not be necessary
while True:
before_folder_contents = os.listdir(scanned_folder) #create a list of all filenames
time.sleep(1) #allow for the file download to take place within the interval of 1 second
after_folder_contents = os.listdir(scanned_folder)
if len(before_folder_contents) != len(after_folder_contents):
modified_file = ... #here, we perform some function that gets the changed file, i.e. the added element between the two lists
output_file.append(modified_file)
break
def download_file():
#I will not write it out in full, but this is the function that downloads a file. It will end once the file has been downloaded.
thread_download_detector = threading.Thread(target=downloaded_file_detector, args=(scanned_folder, variable_function))
thread_download_file = threading.Thread(target=download_file)
thread_download_detector.start()
thread_download_file.start()
#The following block of code will effectively pause execution until the threads have completed
while True:
if len(output_file) != 0:
break
else:
time.sleep(1) #check to see if the two threads have completed ever 1 second
或者，您可以使用 threading.Event 对象并在其中一个线程函数停止运行后设置它，以便查看何时检查下载的文件。这可能是更有效/“pythonic”的做事方式。
我希望这对以后遇到这个问题的人有所帮助。对于此类工作，请查看线程库和 threading.Event 对象，因为这些是（根据我的经验）在多个后续运行的进程之间进行通信的最佳方式。