假如使用Process创建子进程，那么在最后的函数调用时需要加上if __name__ == "__main__":语句，否则会报错。

未使用该语句

代码示例

from multiprocessing import Process


def test_input():
    print("start print info!")


Process(target=test_input).start()

结果示例

RuntimeError: 
        An attempt has been made to start a new process before the
        current process has finished its bootstrapping phase.

        This probably means that you are not using fork to start your
        child processes and you have forgotten to use the proper idiom
        in the main module:

            if __name__ == '__main__':
                freeze_support()
                ...

        The "freeze_support()" line can be omitted if the program
        is not going to be frozen to produce an executable.

使用该语句

代码示例

from multiprocessing import Process


def test_input():
    print("start print info!")


if __name__ == '__main__':
    Process(target=test_input).start()

结果示例

start print info!

Process finished with exit code 0