invalid index of a 0-dim tensor. Use tensor.item() to convert a 0-dim tensor to a python number

提示 Use tensor.item() to convert a 0-dim tensor to a Python number

原语句：running_loss+=loss.data[0]

修改后：running_loss+=loss.item()

报错原因：版本升级

pytorch代码从0.3版本升级版本后的错误