为什么我的 PyTorch ModuleList object 在分配为 class 变量后变成了一个“函数”object？

Question

I really need your help with something annoying that I can't explain. I am fairly new to PyTorch and want to implementa a Module that requires the usage of ModuleList. However after instantiation of an empty ModuleList object, I can't use its append-method. Why?

self.modules = torch.nn.ModuleList([])
print(type(self.modules), type(torch.nn.ModuleList())) # -> <class 'method'> <class 'torch.nn.modules.container.ModuleList'>
for m in range(len(self.module_sizes)):

        prev_channels = 0 if m == 0 else self.module_out_channels[-m]
        vgg19_channels = self.vgg19_layer_channels[-(m+1)]
        module_out_channels = self.module_out_channels[-(m+1)]
        module_size = self.module_sizes[-(m+1)]

        self.modules.append(
            GeneratorModule(prev_channels=prev_channels, vgg19_channels=vgg19_channels, out_channels=module_out_channels, module_size=module_size, initial=(m==0))
            )

The error message says:

  File "main.py", line 90, in __init__
    self.modules.append(
AttributeError: 'function' object has no attribute 'append'

So far so good. I assume that as soon as I assign a ModuleList as a class variable to my custom nn.Module subclass, it becomes a 'function' object. So I changed the code in a way that the ModuleList is assigned to self.modules after the appending loop. But then it throws another error in a later piece of code, where it says:

for m, module in enumerate(self.modules):
     pass

TypeError: 'method' object is not iterable

I know that this should work, since I found other people do it this way on the inte.net.

I would be so happy if any more experienced PyTorch programmer can help me out. Thanks in advance!

Answer 1

Actually the problem is different. As you can see torch.nn.ModuleList has append and other list-like methods so it should work. No, it doesn't "change" to "function" object, that would be pretty unintuitive for everyone.

What's going on instead is PyTorch's torch.nn.Module has a few methods which you inherit, which includesmodules (it allows you to iterate over modules contained in torch.nn.Module instance).

Just rename your self.modules to self.module_list and you are all good.