.item()

import torch
b = []
c = []
a = torch.tensor((9))
print(a)
b.append(a)
print(b)
c.append(a.item())
print(c)

结果：
a： tensor(0)
b： [tensor(0)]
c： [0]

caution: only one element tensors can be converted to Python scalars--->a只能有一个元素