python – Threads中的subprocess.Popen

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我有很多文件(超过4000个),我想同时加载到PostgreSQL中.我已将它们分成4个不同的文件列表,我想要一个线程迭代加载数据的每个列表.

我遇到的问题是我使用os.system来调用加载程序但这会阻止其他线程同时运行.如果我使用subprocess.Popen然后它们同时运行但是线程认为它们已经完成了execeuting,所以移动到我的脚本的下一部分.

我这样做是对的吗？或者是否有更好的方法从线程内调用子进程.

def thread1Load(self, thread1fileList):
    connectionstring = settings.connectionstring
    postgreshost = settings.postgreshost
    postgresdatabase = settings.postgresdatabase
    postgresport = settings.postgresport
    postgresusername = settings.postgresusername
    postgrespassword = settings.postgrespassword

    tablename = None
    encoding = None
    connection = psycopg2.connect(connectionstring)

    for filename in thread1fileList:
        load_cmd = #load command
        run = subprocess.Popen(load_cmd, shell=True)
    print "finished loading thread 1"


def thread2Load(self, thread2fileList):
    connectionstring = settings.connectionstring
    postgreshost = settings.postgreshost
    postgresdatabase = settings.postgresdatabase
    postgresport = settings.postgresport
    postgresusername = settings.postgresusername
    postgrespassword = settings.postgrespassword

    tablename = None

    connection = psycopg2.connect(connectionstring)
    for filename in thread2fileList:
        load_cmd = #load command            
        run = subprocess.Popen(load_cmd, shell=True)
    print "finished loading thread 2"


def thread3Load(self, thread3fileList):
    connectionstring = settings.connectionstring
    postgreshost = settings.postgreshost
    postgresdatabase = settings.postgresdatabase
    postgresport = settings.postgresport
    postgresusername = settings.postgresusername
    postgrespassword = settings.postgrespassword

    tablename = None
    connection = psycopg2.connect(connectionstring)

    for shapefilename in thread3fileList:
        load_cmd = #load command
        run = subprocess.Popen(load_cmd, shell=True)
    print "finished loading thread 3"

def thread4Load(self, thread4fileList):
    connectionstring = settings.connectionstring
    postgreshost = settings.postgreshost
    postgresdatabase = settings.postgresdatabase
    postgresport = settings.postgresport
    postgresusername = settings.postgresusername
    postgrespassword = settings.postgrespassword

    tablename = None

    connection = psycopg2.connect(connectionstring)

    for filename in thread4fileList:
        load_cmd = #load command
        run = subprocess.Popen(load_cmd, shell=True)

    print "finished loading thread 4"


def finishUp(self):
    print 'finishing up'


def main():
load = Loader()

thread1 = threading.Thread(target=(load.thread1Load), args=(thread1fileList, ))
thread2 = threading.Thread(target=(load.thread2Load), args=(thread2fileList, ))
thread3 = threading.Thread(target=(load.thread3Load), args=(thread3fileList, ))
thread4 = threading.Thread(target=(load.thread4Load), args=(thread4fileList, ))
threads = [thread1, thread2, thread3, thread4]
for thread in threads:
    thread.start()
    thread.join()


load.finishUp(connectionstring)

if __name__ == '__main__':
main()

解决方法:

> Don’t repeat yourself.一个threadLoad方法就足够了.这样,如果您需要修改方法中的某些内容,则无需在4个不同的位置进行相同的修改.
>使用run.communicate()阻止,直到子进程完成.
>这将启动一个线程,然后阻塞直到该线程完成,然后
启动另一个线程等：

for thread in threads:
    thread.start()
    thread.join()

相反,首先启动所有线程,然后加入所有线程：

for thread in threads:
    thread.start()
for thread in threads:
    thread.join()

import subprocess
import threading


class Loader(object):
    def threadLoad(self, threadfileList):
        connectionstring = settings.connectionstring
        ...
        connection = psycopg2.connect(connectionstring)

        for filename in threadfileList:
            load_cmd =  # load command
            run = subprocess.Popen(load_cmd, shell=True)
            # block until subprocess is done
            run.communicate()
        name = threading.current_thread().name
        print "finished loading {n}".format(n=name)

    def finishUp(self):
        print 'finishing up'


def main():
    load = Loader()
    threads = [threading.Thread(target=load.threadLoad, args=(fileList, ))
               for fileList in (thread1fileList, thread2fileList,
                                thread3fileList, thread4fileList)]
    for thread in threads:
        thread.start()
    for thread in threads:
        thread.join()

    load.finishUp(connectionstring)

if __name__ == '__main__':
    main()

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