Python 脚本使用 while 循环来不断更新作业脚本并多处理队列中的任务

Question

我正在尝试编写一个扫描文件夹并收集更新的 SQL 脚本的 python 脚本，然后自动为 SQL 脚本提取数据。在代码中，一个while循环正在扫描新的SQL文件，并发送到数据拉取函数。我无法理解如何使用 while 循环创建动态队列，但也有多进程来运行队列中的任务。

以下代码存在一个问题，即 while 循环迭代在移动到下一次迭代之前会处理一个很长的作业，并收集其他作业来填充空闲的处理器。

更新:

1. 感谢@pbacterio 发现了这个错误，现在错误消息已经消失了。更改代码后，python 代码可以在一次迭代中获取所有作业脚本，并将脚本分发到四个处理器。但是，要进行下一次迭代，扫描并提交新添加的作业脚本，它将被一个很长的作业挂起。知道如何重构代码吗？

2. 我终于找到了解决方案，请参阅下面的答案。原来我要找的是

   the_queue = 队列()
   the_pool = Pool(4, worker_main,(the_queue,))

3. 对于那些偶然发现类似想法的人，以下是这个自动化脚本的整个架构，它将共享驱动器转换为“用于 SQL 拉取的服务器”或任何其他作业队列“服务器”。

   一个。 python 脚本 auto_data_pull.py 如答案所示。您需要添加自己的工作职能。

   b.具有以下内容的“批处理脚本”:

   启动 C:\Anaconda2\python.exe C:\Users\bin\auto_data_pull.py

   c。添加由启动计算机触发的任务，运行“批处理脚本”就这样。有用。

Python 代码:

from glob import glob
import os, time
import sys
import CSV
import re
import subprocess
import pandas as PD
import pypyodbc
from multiprocessing import Process, Queue, current_process, freeze_support

#
# Function run by worker processes
#

def worker(input, output):
    for func, args in iter(input.get, 'STOP'):
        result = compute(func, args)
        output.put(result)

#
# Function used to compute result
#

def compute(func, args):
    result = func(args)
    return '%s says that %s%s = %s' % \
        (current_process().name, func.__name__, args, result)


def query_sql(sql_file): #test func
    #jsl file processing and SQL querying, data table will be saved to csv.
    fo_name = os.path.splitext(sql_file)[0] + '.csv'
    fo = open(fo_name, 'w')
    print sql_file
    fo.write("sql_file {0} is done\n".format(sql_file))
    return "Query is done for \n".format(sql_file)


def check_files(path):
    """
    arguments -- root path to monitor
    returns   -- dictionary of {file: timestamp, ...}
    """
    sql_query_dirs = glob(path + "/*/IDABox/")

    files_dict = {}
    for sql_query_dir in sql_query_dirs:
        for root, dirs, filenames in os.walk(sql_query_dir):
            [files_dict.update({(root + filename): os.path.getmtime(root + filename)}) for 
                     filename in filenames if filename.endswith('.jsl')]
    return files_dict


##### working in single thread
def single_thread():
    path = "Y:/"

    before = check_files(path)
    sql_queue  = [] 

    while True:
        time.sleep(3)
        after = check_files(path)
        added = [f for f in after if not f in before]
        deleted = [f for f in before if not f in after]
        overlapped = list(set(list(after)) & set(list(before)))
        updated = [f for f in overlapped if before[f] < after[f]]  

        before = after

        sql_queue = added + updated
        # print sql_queue
        for sql_file in sql_queue:
            try:
                query_sql(sql_file)
            except:
                pass


##### not working in queue
def multiple_thread():

    NUMBER_OF_PROCESSES = 4
    path = "Y:/"

    sql_queue  = [] 
    before = check_files(path) # get the current dictionary of sql_files
    task_queue = Queue()
    done_queue = Queue()

    while True:         #while loop to check the changes of the files
        time.sleep(5)
        after = check_files(path)
        added = [f for f in after if not f in before]
        deleted = [f for f in before if not f in after]
        overlapped = list(set(list(after)) & set(list(before)))
        updated = [f for f in overlapped if before[f] < after[f]]  

        before = after  
        sql_queue = added + updated   

        TASKS = [(query_sql, sql_file) for sql_file in sql_queue]
        # Create queues

        #submit task
        for task in TASKS:
            task_queue.put(task)

        for i in range(NUMBER_OF_PROCESSES):
                p = Process(target=worker, args=(task_queue, done_queue)).start()          
            # try:
            #     p = Process(target=worker, args=(task_queue))
            #     p.start()

            # except:
            #     pass 

        # Get and print results
        print 'Unordered results:'
        for i in range(len(TASKS)):
            print '\t', done_queue.get()
        # Tell child processes to stop
        for i in range(NUMBER_OF_PROCESSES):
            task_queue.put('STOP')        

# single_thread()
if __name__ == '__main__':
    # freeze_support()
    multiple_thread()

引用:

1. 使用 python 脚本监控文件更改:http://timgolden.me.uk/python/win32_how_do_i/watch_directory_for_changes.html
2. 多处理:
   https://docs.python.org/2/library/multiprocessing.html

Answer 1

multiple_thread()中的sql_file在哪里定义

multiprocessing.Process(target=query_sql, args=(sql_file)).start()

您还没有在方法中定义 sql_file，而且您在 for 循环中使用了该变量。变量的作用域仅限于 for 循环。