有时会遇到此类问题

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.

只需要在所运行的代码前面加上if __name__=="__main__":