代码如下：

'''
Parallel data loading functions  并行数据加载功能
'''
import sys
import time
import theano
import numpy as np
import traceback
from PIL import Image
from six.moves import queue
from multiprocessing import Process, Event

from lib.config import cfg
from lib.data_augmentation import preprocess_img
from lib.data_io import get_voxel_file, get_rendering_file
from lib.binvox_rw import read_as_3d_array


def print_error(func):
    '''Flush out error messages. Mainly used for debugging separate processes'''
    #清除错误消息。主要用于调试单独的过程

    def func_wrapper(*args, **kwargs):
        try:
            return func(*args, **kwargs)
        except:
            traceback.print_exception(*sys.exc_info())
            sys.stdout.flush()

    return func_wrapper


class DataProcess(Process):

    def __init__(self, data_queue, data_paths, repeat=True):
        '''
        data_queue : Multiprocessing queue多处理队列
        data_paths : list of data and label pair used to load data用于加载数据的数据列表和标签对
        repeat : if set True, return data until exit is set 重复：如果设置为真，返回数据直到设置了退出
        '''
        super(DataProcess, self).__init__()
        # Queue to transfer the loaded mini batches队列以传输加载的小批次
        self.data_queue = data_queue
        self.data_paths = data_paths
        self.num_data = len(data_paths)
        self.repeat = repeat

        # Tuple of data shape数据形状的元组
        self.batch_size = cfg.CONST.BATCH_SIZE
        self.exit = Event()
        self.shuffle_db_inds()

    def shuffle_db_inds(self):
        # Randomly permute the training roidb 随机排列训练ROIDB
        # (roidb是由字典组成的list,包含了该图片索引所包含的roi信息)
        if self.repeat:
            self.perm = np.random.permutation(np.arange(self.num_data))
        else:
            self.perm = np.arange(self.num_data)
        self.cur = 0

    def get_next_minibatch(self):
        if (self.cur + self.batch_size) >= self.num_data and self.repeat:
            self.shuffle_db_inds()

        db_inds = self.perm[self.cur:min(self.cur + self.batch_size, self.num_data)]
        self.cur += self.batch_size
        return db_inds

    def shutdown(self):
        self.exit.set()

    @print_error
    def run(self):
        iteration = 0
        # Run the loop until exit flag is set运行循环，直到设置了退出标志
        while not self.exit.is_set() and self.cur <= self.num_data:
            # Ensure that the network sees (almost) all data per epoch
            # 确保网络可以（几乎）看到每个时代的所有数据
            db_inds = self.get_next_minibatch()

            data_list = []
            label_list = []
            for batch_id, db_ind in enumerate(db_inds):
                datum = self.load_datum(self.data_paths[db_ind])
                label = self.load_label(self.data_paths[db_ind])

                data_list.append(datum)
                label_list.append(label)

            batch_data = np.array(data_list).astype(np.float32)
            batch_label = np.array(label_list).astype(np.float32)

            # The following will wait until the queue frees以下操作将等待队列释放
            self.data_queue.put((batch_data, batch_label), block=True)
            iteration += 1

    def load_datum(self, path):
        pass

    def load_label(self, path):
        pass


class ReconstructionDataProcess(DataProcess):

    def __init__(self, data_queue, category_model_pair, background_imgs=[], repeat=True,
                 train=True):
        self.repeat = repeat
        self.train = train
        self.background_imgs = background_imgs
        super(ReconstructionDataProcess, self).__init__(
            data_queue, category_model_pair, repeat=repeat)

    @print_error    #先执行修饰器函数
    def run(self):
        # set up constants设置常量
        img_h = cfg.CONST.IMG_W
        img_w = cfg.CONST.IMG_H
        n_vox = cfg.CONST.N_VOX

        # This is the maximum number of views 这是最大视图数
        n_views = cfg.CONST.N_VIEWS

        while not self.exit.is_set() and self.cur <= self.num_data:
            # To insure that the network sees (almost) all images per epoch
            # 以确保网络能够（几乎）看到每个时代的所有图像
            db_inds = self.get_next_minibatch()

            # We will sample # views 我们将采样视图
            if cfg.TRAIN.RANDOM_NUM_VIEWS:
                curr_n_views = np.random.randint(n_views) + 1
            else:
                curr_n_views = n_views

            # This will be fed into the queue. create new batch everytime
            # 这将被送入队列。每次创建新批
            batch_img = np.zeros(
                (curr_n_views, self.batch_size, 3, img_h, img_w), dtype=theano.config.floatX)
            batch_voxel = np.zeros(
                (self.batch_size, n_vox, 2, n_vox, n_vox), dtype=theano.config.floatX)

            # load each data instance 加载每个数据实例
            for batch_id, db_ind in enumerate(db_inds):
                category, model_id = self.data_paths[db_ind]
                image_ids = np.random.choice(cfg.TRAIN.NUM_RENDERING, curr_n_views)

                # load multi view images 加载多视图图像
                for view_id, image_id in enumerate(image_ids):
                    im = self.load_img(category, model_id, image_id)
                    # channel, height, width 通道，高度，宽度
                    batch_img[view_id, batch_id, :, :, :] = \
                        im.transpose((2, 0, 1)).astype(theano.config.floatX)

                voxel = self.load_label(category, model_id)
                voxel_data = voxel.data

                batch_voxel[batch_id, :, 0, :, :] = voxel_data < 1
                batch_voxel[batch_id, :, 1, :, :] = voxel_data

            # The following will wait until the queue frees 以下操作将等待队列释放
            self.data_queue.put((batch_img, batch_voxel), block=True)

        print('Exiting')

    def load_img(self, category, model_id, image_id):
        image_fn = get_rendering_file(category, model_id, image_id)
        im = Image.open(image_fn)

        t_im = preprocess_img(im, self.train)
        return t_im

    def load_label(self, category, model_id):
        voxel_fn = get_voxel_file(category, model_id)
        with open(voxel_fn, 'rb') as f:
            voxel = read_as_3d_array(f)

        return voxel


def kill_processes(queue, processes):
    print('Signal processes')
    for p in processes:
        p.shutdown()

    print('Empty queue')
    while not queue.empty():
        time.sleep(0.5)
        queue.get(False)

    print('kill processes')
    for p in processes:
        p.terminate()


def make_data_processes(queue, data_paths, num_workers, repeat=True, train=True):
    '''
    Make a set of data processes for parallel data loading. 为并行数据加载创建一组数据处理。
    '''
    processes = []
    for i in range(num_workers):
        process = ReconstructionDataProcess(queue, data_paths, repeat=repeat, train=train)
        process.start()
        processes.append(process)
    return processes


def get_while_running(data_process, data_queue, sleep_time=0):
    while True:
        time.sleep(sleep_time)
        try:
            batch_data, batch_label = data_queue.get_nowait()
        except queue.Empty:
            if not data_process.is_alive():
                break
            else:
                continue
        yield batch_data, batch_label


def test_process():
    from multiprocessing import Queue
    from lib.config import cfg
    from lib.data_io import category_model_id_pair

    cfg.TRAIN.PAD_X = 10
    cfg.TRAIN.PAD_Y = 10

    data_queue = Queue(2)
    category_model_pair = category_model_id_pair(dataset_portion=[0, 0.1])

    data_process = ReconstructionDataProcess(data_queue, category_model_pair)
    data_process.start()
    batch_img, batch_voxel = data_queue.get()

    kill_processes(data_queue, [data_process])


if __name__ == '__main__':
    test_process()

报错如下：
  File "/home/nvidia/Downloads/3D-R2N2/lib/data_process.py", line 178, in kill_processes
    for p in processes:
TypeError: 'NoneType' object is not iterable

ok，发现问题了，不是这个代码的问题，是文件调用的问题