在Windows上，子进程将在启动时导入(即执行)主模块。你需要在主模块中插入一个if __name__ == '__main__':守卫，以避免递归地创建子进程。

修改testMain.py:

import parallelTestModule

if __name__ == '__main__':    
    extractor = parallelTestModule.ParallelExtractor()
    extractor.runInParallel(numProcesses=2, numThreads=4)

尝试将代码放在testMain.py中的主函数中

import parallelTestModule

if __name__ ==  '__main__':
  extractor = parallelTestModule.ParallelExtractor()
  extractor.runInParallel(numProcesses=2, numThreads=4)

查看文档:

"For an explanation of why (on Windows) the if __name__ == '__main__' 
part is necessary, see Programming guidelines."

这说

确保主模块可以被新的Python安全地导入 解释器，而不会引起意外的副作用(例如启动一个 新流程)”。

．.． 通过使用if __name__ == '__main__'

虽然前面的答案是正确的，但有一个小问题需要说明。

如果你的主模块导入了另一个模块，其中的全局变量或类成员变量被定义并初始化为(或使用)一些新对象，你可能必须以相同的方式设置导入条件:

if __name__ ==  '__main__':
  import my_module

正如@Ofer所说，当你使用其他库或模块时，你应该在if __name__ == '__main__'中导入它们:

所以，在我的例子中，结尾是这样的:

if __name__ == '__main__':       
    import librosa
    import os
    import pandas as pd
    run_my_program()

在我的例子中，这是代码中的一个简单错误，在创建变量之前使用了一个变量。在尝试上述解决方案之前，值得检查一下。为什么我得到这个特殊的错误消息，天知道。

你好，这是我的多进程结构

from multiprocessing import Process
import time


start = time.perf_counter()


def do_something(time_for_sleep):
    print(f'Sleeping {time_for_sleep} second...')
    time.sleep(time_for_sleep)
    print('Done Sleeping...')



p1 = Process(target=do_something, args=[1])
p2 = Process(target=do_something, args=[2])


if __name__ == '__main__':
    p1.start()
    p2.start()

    p1.join()
    p2.join()

    finish = time.perf_counter()
    print(f'Finished in {round(finish-start,2 )} second(s)')

你不必在if __name__ == '__main__':中导入，只需运行你希望在里面运行的程序

下面的解决方案应该适用于python multiprocessing和pytorch multiprocessing。

正如其他答案提到的修复是有if __name__ == '__main__':但我在确定从哪里开始时遇到了几个问题，因为我正在使用几个脚本和模块。当我可以在main内部调用我的第一个函数时，然后在它开始创建多个进程之前的一切(不确定为什么)。

将它放在第一行(甚至在导入之前)可以工作。只调用第一个函数返回超时错误。下面是我的代码和multiprocessing的第一个文件调用几个函数后使用，但把主要放在第一个似乎是这里唯一的修复。

if __name__ == '__main__':
    from mjrl.utils.gym_env import GymEnv
    from mjrl.policies.gaussian_mlp import MLP
    from mjrl.baselines.quadratic_baseline import QuadraticBaseline
    from mjrl.baselines.mlp_baseline import MLPBaseline
    from mjrl.algos.npg_cg import NPG
    from mjrl.algos.dapg import DAPG
    from mjrl.algos.behavior_cloning import BC
    from mjrl.utils.train_agent import train_agent
    from mjrl.samplers.core import sample_paths
    import os
    import json
    import mjrl.envs
    import mj_envs
    import time as timer
    import pickle
    import argparse

    import numpy as np 

    # ===============================================================================
    # Get command line arguments
    # ===============================================================================

    parser = argparse.ArgumentParser(description='Policy gradient algorithms with demonstration data.')
    parser.add_argument('--output', type=str, required=True, help='location to store results')
    parser.add_argument('--config', type=str, required=True, help='path to config file with exp params')
    args = parser.parse_args()
    JOB_DIR = args.output
    if not os.path.exists(JOB_DIR):
        os.mkdir(JOB_DIR)
    with open(args.config, 'r') as f:
        job_data = eval(f.read())
    assert 'algorithm' in job_data.keys()
    assert any([job_data['algorithm'] == a for a in ['NPG', 'BCRL', 'DAPG']])
    job_data['lam_0'] = 0.0 if 'lam_0' not in job_data.keys() else job_data['lam_0']
    job_data['lam_1'] = 0.0 if 'lam_1' not in job_data.keys() else job_data['lam_1']
    EXP_FILE = JOB_DIR + '/job_config.json'
    with open(EXP_FILE, 'w') as f:
        json.dump(job_data, f, indent=4)

    # ===============================================================================
    # Train Loop
    # ===============================================================================

    e = GymEnv(job_data['env'])
    policy = MLP(e.spec, hidden_sizes=job_data['policy_size'], seed=job_data['seed'])
    baseline = MLPBaseline(e.spec, reg_coef=1e-3, batch_size=job_data['vf_batch_size'],
                           epochs=job_data['vf_epochs'], learn_rate=job_data['vf_learn_rate'])

    # Get demonstration data if necessary and behavior clone
    if job_data['algorithm'] != 'NPG':
        print("========================================")
        print("Collecting expert demonstrations")
        print("========================================")
        demo_paths = pickle.load(open(job_data['demo_file'], 'rb'))

        ########################################################################################
        demo_paths = demo_paths[0:3]
        print (job_data['demo_file'], len(demo_paths))
        for d in range(len(demo_paths)):
            feats = demo_paths[d]['features']
            feats = np.vstack(feats)
            demo_paths[d]['observations'] = feats

        ########################################################################################

        bc_agent = BC(demo_paths, policy=policy, epochs=job_data['bc_epochs'], batch_size=job_data['bc_batch_size'],
                      lr=job_data['bc_learn_rate'], loss_type='MSE', set_transforms=False)

        in_shift, in_scale, out_shift, out_scale = bc_agent.compute_transformations()
        bc_agent.set_transformations(in_shift, in_scale, out_shift, out_scale)
        bc_agent.set_variance_with_data(out_scale)

        ts = timer.time()
        print("========================================")
        print("Running BC with expert demonstrations")
        print("========================================")
        bc_agent.train()
        print("========================================")
        print("BC training complete !!!")
        print("time taken = %f" % (timer.time() - ts))
        print("========================================")

        # if job_data['eval_rollouts'] >= 1:
        #     score = e.evaluate_policy(policy, num_episodes=job_data['eval_rollouts'], mean_action=True)
        #     print("Score with behavior cloning = %f" % score[0][0])

    if job_data['algorithm'] != 'DAPG':
        # We throw away the demo data when training from scratch or fine-tuning with RL without explicit augmentation
        demo_paths = None

    # ===============================================================================
    # RL Loop
    # ===============================================================================

    rl_agent = DAPG(e, policy, baseline, demo_paths,
                    normalized_step_size=job_data['rl_step_size'],
                    lam_0=job_data['lam_0'], lam_1=job_data['lam_1'],
                    seed=job_data['seed'], save_logs=True
                    )

    print("========================================")
    print("Starting reinforcement learning phase")
    print("========================================")


    ts = timer.time()
    train_agent(job_name=JOB_DIR,
                agent=rl_agent,
                seed=job_data['seed'],
                niter=job_data['rl_num_iter'],
                gamma=job_data['rl_gamma'],
                gae_lambda=job_data['rl_gae'],
                num_cpu=job_data['num_cpu'],
                sample_mode='trajectories',
                num_traj=job_data['rl_num_traj'],
                num_samples= job_data['rl_num_samples'],
                save_freq=job_data['save_freq'],
                evaluation_rollouts=job_data['eval_rollouts'])
    print("time taken = %f" % (timer.time()-ts))

我也遇到了同样的问题。@ofter方法是正确的，因为有一些细节需要注意。以下是我修改成功的调试代码，请参考:

if __name__ == '__main__':
    import matplotlib.pyplot as plt
    import numpy as np
    def imgshow(img):
        img = img / 2 + 0.5
        np_img = img.numpy()
        plt.imshow(np.transpose(np_img, (1, 2, 0)))
        plt.show()

    dataiter = iter(train_loader)
    images, labels = dataiter.next()

    imgshow(torchvision.utils.make_grid(images))
    print(' '.join('%5s' % classes[labels[i]] for i in range(4)))

声明一下，我没有子程序，我只有一个主程序，但我遇到了和你一样的问题。这表明当在程序段中间导入Python库文件时，我们应该添加:

if __name__ == '__main__':

在yolo v5中使用python 3.8.5

if __name__ == '__main__':
    from yolov5 import train
    train.run()

我在下面这段非常简单的代码中尝试了上面提到的技巧。但我仍然无法阻止它在任何使用Python 3.8/3.10的windows机器上重置。如果你能告诉我哪里错了，我将非常感激。

print('script reset')

def do_something(inp):
    print('Done!')

if __name__ == '__main__':
    from multiprocessing import Process, get_start_method
    print('main reset')
    print(get_start_method())
    Process(target=do_something, args=[1]).start()
    print('Finished')

输出显示:

script reset
main reset
spawn
Finished
script reset
Done!

更新:

据我所知，你们并没有阻止包含__main__或.start()的脚本重置(这在Linux中不会发生)，而是建议解决方案，这样我们就不会看到重置。我们必须尽量减少所有的导入，并将它们分别放在每个函数中，但相对于Linux，它仍然很慢。