python - Pytorch教程代码错误: "NameError: name ' net' is not defined"

Question

代码来自tutorial for PyTorch .我正在使用 Google Collabs notebook 来运行代码。

import torch
import torch.nn as nn
import torch.nn.functional as F

class Net(nn.Module):

  def __init__(self):
    super(Net, self).__init__()
    self.conv1 = nn.Conv2d(1, 6, 3)
    self.conv2 = nn.Conv2d(6, 16, 3)
    self.fc1 = nn.Linear(16 * 6 * 6, 120)
    self.fc2 = nn.Linear(120, 84)
    self.fc3 = nn.Linear(84, 10)

  def forward(self, x):
    x = F.max_pool2d(F.relu(self.conv1(x)), (2,2))
    x = F.max_pool2d(F.relu(self.conv2(x)), 2)
    x = x.view(-1, self.num_flat_features(x))
    x = F.relu(self.fc1(x))
    x = F.relu(self.fc2(x))
    x = self.fc3(x)
    return x
  
  def num_flat_features(self, x):
    size = x.size()[1:]
    num_features = 1
    for s in size:
      num_features *= s
    return num_features
  
  net = Net()
  print(net)

# The code works up until here. It's the following chunk that returns an error. 
params = list(net.parameters())
print(len(params))
print(params[0].size())

错误是:

NameError                                 Traceback (most recent call last)

<ipython-input-17-ad79a1eff4f3> in <module>()
     32   print(net)
     33 
---> 34 params = list(net.parameters())
     35 print(len(params))
     36 print(params[0].size())

NameError: name 'net' is not defined

教程说输出应该是这样的:

10
torch.Size([6, 1, 3, 3])

在我看来，net 已定义，所以我不清楚为什么会发生此错误。我一开始就不是 Python 专家，所以也许我遗漏了一些明显的东西。

Answer 1

您的缩进意味着这些行:

  net = Net()
  print(net)

是 Net 类的一部分，因为它们与类定义在同一范围内。

将它们移到该类定义之外(即，删除这些行的空白缩进)它应该可以工作。

我还建议改用四个空格而不是两个缩进，以使 Python 的空白更易于扫描。