等待两个子进程完成但不一定要先等待

Question

我正在编写一个创建两个新进程的程序，并且必须等待它们都完成才能继续。如何启动两个进程并让程序等待两者退出？考虑伪代码：

我目前有：

create_process("program1.exe").wait()
create_process("program2.exe").wait()

这很好，因为program2可以与program1同时运行。

create_process("program1.exe")
create_process("program2.exe").wait()

这可能是错误的，因为 program1 可能需要比 program2 更长的时间。

我对通用解决方案感兴趣，我敢打赌已经发明了算法或设计模式来处理这些问题。但是为了给这个问题添加上下文，我正在编写一个调用 pgsql2shp.exe 两次的 Python 脚本，以将两个表从数据库导出到本地机器，然后执行一个交集。该脚本使用 Python 2.7 编写，使用 subprocess.popen

Answer 1

如何使用线程？ 如果你启动几个线程，每个线程可以独立运行，当它们完成时你可以加入线程。

试试这样的代码：（这段代码被大量注释，以便您可以了解正在发生的事情）

# Import threading
import threading

# Create a handler class.
# Each instance will run in it's own independent thread
class ThreadedHandler (threading.Thread):

    # This method is called when you call threadInstance.start()
    def run(self):

        # Run your sub process and wait for it
        # How you run your process is up to you
        create_process(self.programName).wait()

# Create a new thread object
thread1 = ThreadedHandler()

# Set your program name so that when the thread is started
# the correct process is run
thread1.programName = 'program1.exe'

# Start the thread
thread1.start()

# Again, create a new thread object for the 2nd program
thread2 = ThreadedHandler()

# Set the program name
thread2.programName = 'program2.exe'

# Start the thread
thread2.start()

# At this point, each program is running independently in separate threads
# Each thread will wait for their respective sub process to complete

# Here, we join both threads. (Wait for both threads to complete)
thread1.join()
thread2.join()

# When we get here, both of our programs are finished and they both ran in parallel