为什么突然在python中杀死线程是一个坏习惯？

Question

我最近一直在阅读和学习线程，以便可以在我的项目中使用它们。我阅读了许多文章，其中大多数人都说突然终止线程是一种不好的做法，但是没有一篇文章我是一名业余程序员，对此我讲得太多了，有人可以举一个例子给我做一个简短的解释，以便我理解这个事实。

@app.before_first_request
def activate_job():
    global files_dict
    global files_meta_dict
    def run_user_job():
        while True:
            USER_QUEUE=User.query.filter_by(processing_status="queued").first()
            if( bool(files_dict) and bool(files_meta_dict) and USER_QUEUE!=None):    //check if dictionaries are empty
                doc_details={}


                print("admin queue is",USER_QUEUE)
                doc_details["id"]=USER_QUEUE.doc_id
                for key,value in files_dict.items():
                    if value==USER_QUEUE.doc_id:                                  //dictionary reverse search
                        doc_details["name"]=key
                        break
                try:
                    doc.main_write([doc_details], USER_QUEUE.email, USER_QUEUE.ref_no, json.loads(USER_QUEUE.user_data))  //parses a document and mails it
                    print("this sends mail")
                    USER_QUEUE.processing_status="processed"
                    db.session.merge(USER_QUEUE)
                    db.session.commit()
                except Exception as e:
                    USER_QUEUE.processing_status="queued"
                    db.session.merge(USER_QUEUE)
                    db.session.commit()
                    print("Exception occured In the User queue thread",e)

    def run_admin_job():
        global files_dict
        global files_meta_dict
        while True:
            ADMIN_QUEUE=User.query.filter(User.status!=0,User.final_mail_sent=="queued").first()

            if( bool(files_dict) and bool(files_meta_dict) and ADMIN_QUEUE!=None):          //check if dictionaries are empty
                print("in if statement")
                doc_details={}
                print("doing admin job")
                doc_details["id"]=ADMIN_QUEUE.doc_id
                for key,value in files_dict.items():
                    if value==ADMIN_QUEUE.doc_id:
                        doc_details["name"]=key                                               //dictionary reverse search
                        break

                if(ADMIN_QUEUE.status!=0):
                    if(ADMIN_QUEUE.status==1):
                        try:
                            start_index,end_index=doc.get_index(ADMIN_QUEUE.parsed_doc_id, "{{Signature}}\n")                 //gets index of "{{Signature}}"
                            print("start index and end index",start_index,end_index)
                            doc.approve_sign(ADMIN_QUEUE.parsed_doc_id,start_index)                                           //places a signature photo to the acquired index
                            doc.download_pdf(ADMIN_QUEUE.parsed_doc_id)                                                       //downloads pdf
                            doc.send_mail_flask_to_user(doc_details["name"],ADMIN_QUEUE.parsed_doc_id,ADMIN_QUEUE.email,True)
                            ADMIN_QUEUE.final_mail_sent="processed"
                            db.session.merge(ADMIN_QUEUE)
                            db.session.commit()
                        except Exception as e:
                            ADMIN_QUEUE.final_mail_sent="queued"
                            db.session.merge(ADMIN_QUEUE)
                            db.session.commit()
                            print("Exception occured at Admin queue thread while approving",e,doc_details,ADMIN_QUEUE.parsed_doc_id)

                    elif(ADMIN_QUEUE.status==-1):
                        doc.send_mail_flask_to_user(doc_details["name"],ADMIN_QUEUE.parsed_doc_id,ADMIN_QUEUE.email,False)
                        ADMIN_QUEUE.final_mail_sent="processed"
                        db.session.merge(ADMIN_QUEUE)
                        db.session.commit()

    admin_thread_queue=threading.Thread(target=run_user_job)
    user_thread_queue=threading.Thread(target=run_admin_job)
    user_thread_queue.start()
    admin_thread_queue.start()