类型错误：传递给 Tensor.__format__ 的格式字符串不受支持

Question

当尝试将旧 PyTorch 编写的代码转换为 1.9 时，我收到此错误：

(fashcomp) [jalal@goku fashion-compatibility]$ python main.py --name test_baseline --learned --l2_embed --datadir ../../../data/fashion/
/scratch3/venv/fashcomp/lib/python3.8/site-packages/torchvision/transforms/transforms.py:310: UserWarning: The use of the transforms.Scale transform is deprecated, please use transforms.Resize instead.
  warnings.warn("The use of the transforms.Scale transform is deprecated, " +
  + Number of params: 3191808
<class 'torch.utils.data.dataloader.DataLoader'>
/scratch3/venv/fashcomp/lib/python3.8/site-packages/torch/nn/functional.py:718: UserWarning: Named tensors and all their associated APIs are an experimental feature and subject to change. Please do not use them for anything important until they are released as stable. (Triggered internally at  /pytorch/c10/core/TensorImpl.h:1156.)
  return torch.max_pool2d(input, kernel_size, stride, padding, dilation, ceil_mode)
Traceback (most recent call last):
  File "main.py", line 329, in <module>
    main()    
  File "main.py", line 167, in main
    train(train_loader, tnet, criterion, optimizer, epoch)
  File "main.py", line 240, in train
    print('Train Epoch: {} [{}/{}]\t'
  File "/scratch3/venv/fashcomp/lib/python3.8/site-packages/torch/_tensor.py", line 561, in __format__
    return object.__format__(self, format_spec)
TypeError: unsupported format string passed to Tensor.__format__

这是代码中有问题的部分：

if batch_idx % args.log_interval == 0:
    print('Train Epoch: {} [{}/{}]\t'
          'Loss: {:.4f} ({:.4f}) \t'
          'Acc: {:.2f}% ({:.2f}%) \t'
          'Emb_Norm: {:.2f} ({:.2f})'.format(
        epoch, batch_idx * num_items, len(train_loader.dataset),
        losses.val, losses.avg, 
        100. * accs.val, 100. * accs.avg, emb_norms.val, emb_norms.avg))

我从这个错误报告中看到，截至两年前，还没有针对这个问题提供解决方案。您对如何解决这个问题有什么建议，或者有任何替代方案吗？

代码来自这里。

Answer 1

torch.Tensor如果您尝试以特定方式格式化 a，则可以重现此错误：

>>> print('{:.2f}'.format(torch.rand(1)))
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-3-ece663be5b5c> in <module>()
----> 1 print('{:.2f}'.format(torch.tensor([1])))

/usr/local/lib/python3.7/dist-packages/torch/_tensor.py in __format__(self, format_spec)
    559         if self.dim() == 0:
    560             return self.item().__format__(format_spec)
--> 561         return object.__format__(self, format_spec)
    562 
    563     def __ipow__(self, other):  # type: ignore[misc]

TypeError: unsupported format string passed to Tensor.__format__

这样做'{}'.format(torch.tensor(1))-即没有任何格式规则 - 将会起作用。

这是因为torch.Tensor没有实现那些特定的格式操作。

一个简单的解决方法是使用以下方法将 转换torch.Tensor为适当的对应类型item：

>>> print('{:.2f}'.format(torch.rand(1).item()))
0.02

您应该将此修改应用于字符串表达式torch.Tensor中涉及的所有内容print：losses.val、losses.avg、accs.val、accs.avg、emb_norms.val和emb_norms.avg?