AttributeError：“ NoneType”对象没有属性“ zero_”

Question

我正在编写如下代码，运行并获得异常：

AttributeError: 'NoneType' object has no attribute 'zero_'

print(w.grad)一无所有

w = Variable(torch.randn(1), requires_grad=True) 
b = Variable(torch.zeros(1), requires_grad=True)
w.grad.zero_()