RuntimeError: output with shape [1, 28, 28] doesn't match the broadcast shape [3, 28, 28]

RuntimeError: output with shape [1, 28, 28] doesn’t match the broadcast shape [3, 28, 28]
在用pytorch导入mnist数据时出现了上述错误，
报错程序：

transform = transforms.Compose([
	transforms.ToTensor(), 
	transforms.Normalize(mean=[0.5, 0.5, 0.5], std=[0.5, 0.5, 0.5])]) 

报错原因：这是因为mnist图像都是灰度图像，只有一个通道，而上面的transforms.Normalize 却对三个通道都归一化了，这肯定会报错，所以只要像下面修改即可：

transform = transforms.Compose([
    transforms.ToTensor(),
    transforms.Normalize((0.1307,), (0.3081,))
    ])