pytorch 如何拼接迭代的tensor

目的：通过for循环得到的多个tensor，最终拼接起来。

>>> import pytorch
>>> input = torch.randn(2,5)
>>> input.unsqueeze_(1)
tensor([[[-0.1127,  0.1031, -1.7152, -0.1951,  0.8266]],
        [[ 0.2320, -0.2719,  1.6631, -1.3010, -0.1101]]])
>>> lt=[]
>>> for t in input:
    	lt.append(t)
>>> lt
[tensor([[-0.1127,  0.1031, -1.7152, -0.1951,  0.8266]]),
 tensor([[ 0.2320, -0.2719,  1.6631, -1.3010, -0.1101]])]
>>> torch.cat(lt,dim=0)
tensor([[-0.1127,  0.1031, -1.7152, -0.1951,  0.8266],
        [ 0.2320, -0.2719,  1.6631, -1.3010, -0.1101]])    	

注意：
假设input的shape是(2, 5)，input中的每个元素要先增加一维，再放入list。

>>> input.unsqueeze_(1)

如果没有这一步的话，就无法得到想要的结果，还可能会报错。

>>> input = torch.randn(2,5)
>>> lt = []
>>> for t in input:
    	lt.append(t)
>>> lt
	[tensor([ 1.3861, -0.3191,  1.2268, -0.2041, -1.6669]),
 	tensor([-0.0951,  1.1444,  0.7381,  0.4155, -0.1998])]    	
>>> torch.cat(lt, dim=0)
	tensor([ 1.3861, -0.3191,  1.2268, -0.2041, -1.6669, -0.0951,  1.1444,  0.7381,  0.4155, -0.1998])
>>> torch.cat(lt, dim=1)
Traceback (most recent call last):
  File "/IPython/core/interactiveshell.py", line 3296, in run_code
    exec(code_obj, self.user_global_ns, self.user_ns)
  File "", line 4, in <module>
    torch.cat(lt, dim=1)
IndexError: Dimension out of range (expected to be in range of [-1, 0], but got 1)

在torch.cat(lt,dim=0)之前，不必将lt转为tensor，否则会报错。
ValueError: only one element tensors can be converted to Python scalars