"""
    DataLoader 加载器：从dataset中取数据
"""
from torch.utils.data import DataLoader
import torchvision
from torch.utils.tensorboard import SummaryWriter

writer = SummaryWriter("logs/07")

# 创建数据集
test_data = torchvision.datasets.CIFAR10(root="./visionData", train=False, transform=torchvision.transforms.ToTensor())
print('数据集的长度是 %s' % len(test_data))

# 加载数据
'''
dataset: 数据集
batch_size: 每次取的数据个数
shuffle: 取数据时是否重新排序
num_workers: 进程数
drop_last: 最后一组数据个数小于batch_size时，是否舍去
'''
test_loader = DataLoader(dataset=test_data, batch_size=64, shuffle=True, num_workers=0, drop_last=False)

img, target = test_data[0]
print(img.shape)
print(target)

step = 0
for datas in test_loader:
    # datas中包含了每一组中所有的img和target,个数为batch_size
    imgs, targets = datas
    # print(imgs.shape)
    # print(targets)
    writer.add_images("07_test_data", imgs, step)
    step = step + 1

print(f'执行了 {step} 次')

writer.close()
print("program is complete")