CODEWITHSUNDEEP
python
user697911
user697911

Reputation: 10531

How is the parameter passed into the constructor?

This code:

class Net(nn.Module):
    def __init__(self):
        super(Net, self).__init__()

        self.conv1 = nn.Conv2d(1,6,5)
        self.conv2 = nn.Conv2d(6, 16, 5)
        self.fc1 = nn.Linear(16*5*5, 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()

input = torch.randn(1,1,32,32)
out = net(input)

print(out)

I am learning python and trying to understand how this constructor works. My questions are these 2 lines:

input = torch.randn(1,1,32,32)
out = net(input)

In the init initialization, I can't see how the 'input' is used for initialization.

Upvotes: 0

Views: 256

Answers (2)

Gaurang Shah
Gaurang Shah

Reputation: 12920

you are not passing an argument to a Class you are passing an argument to object. There is difference.

Following example shows how to achieve this. You need to implement __call__ method. 

class CallableClass:
    def __init__(self):
        pass


    def __call__(self, *args, **kwargs):
        print(args)


class Net(CallableClass):
    def __init__(self):
        super(Net, self).__init__()
        pass

net = Net()
net(100)

Upvotes: 0

stefan
stefan

Reputation: 248

net = Net()

calls the __init__ method without a argument.

out = net(input)

calls the __call__ method with input as argument. Since Net does not implemented this, it must be implemented in the base class nn.Module

here you can find the sources of nn.Module and there is __call__ defined with input as parameter.

Upvotes: 1

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