如何在Python中从ThreadPoolExecutor进程返回列表

我试图从Python中的ThreadPoolExecutor进程返回一个列表,但在这种情况下,该列表“有效”,在运行完毕后仍为空。

其余的代码都能正常工作(主要是因为,当我尝试从太多的类中提取时,它有时会偶尔抛出“malloc:不正确的校验和”或“分段错误”错误)。

无论哪种方式,我都需要能够将每个循环的所有结果放入一个列表中,并在主函数末尾返回。

我根据注释修改了代码,只是为了让它尽可能简单。

from googleapiclient.discovery import build
from google.oauth2 import service_account as sa
from datetime import datetime,timedelta
import time
import concurrent.futures as cf

key = 'test.json'
email = 'jj@school.com'

works = []

scopes = [
    "https://www.googleapis.com/auth/spreadsheets",
    "https://www.googleapis.com/auth/classroom.courses",
    "https://www.googleapis.com/auth/classroom.coursework.me",
    "https://www.googleapis.com/auth/classroom.coursework.students",
]

cr = sa.Credentials.from_service_account_file(
  key, scopes=scopes).with_subject(email)

sh = build('sheets', 'v4', credentials=cr).spreadsheets()
cl = build('classroom', 'v1', credentials=cr)


def listClasses():
  semdate = "2020/08/01"
  cr1 = datetime.strptime(semdate, '%Y/%m/%d').date()
  pr1 = "profe@school.edu.mx"
  arr1 = []

  re1 = cl.courses().list(
    teacherId=pr1,
    courseStates="ACTIVE"
    ).execute()
  courses = re1.get('courses', [])

  for i in courses:
    ct = i['creationTime'][:10].replace("-","/")
    cr2 = datetime.strptime(ct,'%Y/%m/%d').date()
    ci = i['id']
    if cr2 > cr1:
      arr1.append(ci)

  return arr1


def lcw(i):
    res1= cl.courses().courseWork().list(courseId=i).execute()
    works = res1.get('courseWork', [])
    if len(works) != 0:
      return works 


def main():
  lcs = listClasses()  

  start = time.perf_counter()

  with cf.ThreadPoolExecutor() as excut:
    x = excut.map(lcw,lcs)
    y = [i.result() for i in x]
    print(y)

  fin = time.perf_counter()
  print(f"Done in {round(fin-start, 2)} seconds")
 

if __name__ == '__main__':
   main()