问题描述
我有一个名为 multi.py 的模块.如果我只是想将 multi.py 作为脚本执行,那么避免在 Windows 上崩溃(产生无限数量的进程)的解决方法是将多处理代码放在:
I have a module named multi.py. If I simply wanted to execute multi.py as a script, then the workaround to avoid crashing on Windows (spawning an infinite number of processes) is to put the multiprocessing code under:
if __name__ == '__main__':
但是,我尝试将它作为模块从另一个脚本导入并调用 multi.start().这如何实现?
However, I am trying to import it as a module from another script and call multi.start(). How can this be accomplished?
# multi.py import multiprocessing def test(x): x**=2 def start(): pool = multiprocessing.Pool(processes=multiprocessing.cpu_count()-2) pool.map(test, (i for i in range(1000*1000))) pool.terminate() print('done.') if __name__ == '__main__': print('runs as a script,',__name__) else: print('runs as imported module,',__name__)
这是我运行的 test.py:
# test.py import multi multi.start()
推荐答案
我不太明白你在问什么.你不需要做任何事情来防止它产生无限多的进程.我只是在 Windows XP 上运行它 --- 导入文件并运行 multi.start() --- 它在几秒钟内完成.
I don't quite get what you're asking. You don't need to do anything to prevent this from spawning infinitely many processes. I just ran it on Windows XP --- imported the file and ran multi.start() --- and it completed fine in a couple seconds.
您必须执行 if __name__=="__main__" 保护的原因是,在 Windows 上,多处理必须导入主脚本才能运行目标函数,这意味着顶部-该文件中的级别模块代码将被执行.仅当顶级模块代码本身尝试生成新进程时,才会出现问题.在您的示例中,顶级模块代码不使用多处理,因此没有无限的进程链.
The reason you have to do the if __name__=="__main__" protection is that, on Windows, multiprocessing has to import the main script in order to run the target function, which means top-level module code in that file will be executed. The problem only arises if that top-level module code itself tries to spawn a new process. In your example, the top level module code doesn't use multiprocessing, so there's no infinite process chain.
现在我明白你的要求了.您不需要保护 multi.py.你需要保护你的主脚本,不管它是什么.如果您遇到崩溃,那是因为在您的主脚本中,您在顶级模块代码中执行 multi.start().您的脚本需要如下所示:
Now I get what you're asking. You don't need to protect multi.py. You need to protect your main script, whatever it is. If you're getting a crash, it's because in your main script you are doing multi.start() in the top level module code. Your script needs to look like this:
import multi if __name__=="__main__": multi.start()
main 脚本中始终需要保护".
The "protection" is always needed in the main script.