PyTorch: How to get the shape of a Tensor as a list of int

Question

In numpy, V.shape gives a tuple of ints of dimensions of V.

In tensorflow V.get_shape().as_list() gives a list of integers of the dimensions of V.

In pytorch, V.size() gives a size object, but how do I convert it to ints?

Asked By: patapouf_ai

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Source

Answer 1

For PyTorch v1.0 and possibly above:

>>> import torch
>>> var = torch.tensor([[1,0], [0,1]])

# Using .size function, returns a torch.Size object.
>>> var.size()
torch.Size([2, 2])
>>> type(var.size())
<class 'torch.Size'>

# Similarly, using .shape
>>> var.shape
torch.Size([2, 2])
>>> type(var.shape)
<class 'torch.Size'>

You can cast any torch.Size object to a native Python list:

>>> list(var.size())
[2, 2]
>>> type(list(var.size()))
<class 'list'>

In PyTorch v0.3 and 0.4:

Simply list(var.size()), e.g.:

>>> import torch
>>> from torch.autograd import Variable
>>> from torch import IntTensor
>>> var = Variable(IntTensor([[1,0],[0,1]]))

>>> var
Variable containing:
 1  0
 0  1
[torch.IntTensor of size 2x2]

>>> var.size()
torch.Size([2, 2])

>>> list(var.size())
[2, 2]

Answered By: alvas

Answer 2

If you’re a fan of NumPyish syntax, then there’s tensor.shape.

In [3]: ar = torch.rand(3, 3)

In [4]: ar.shape
Out[4]: torch.Size([3, 3])

# method-1
In [7]: list(ar.shape)
Out[7]: [3, 3]

# method-2
In [8]: [*ar.shape]
Out[8]: [3, 3]

# method-3
In [9]: [*ar.size()]
Out[9]: [3, 3]

P.S.: Note that tensor.shape is an alias to tensor.size(), though tensor.shape is an attribute of the tensor in question whereas tensor.size() is a function.

Answered By: kmario23

Answer 3

Previous answers got you list of torch.Size
Here is how to get list of ints

listofints = [int(x) for x in tensor.shape]

Answered By: vozman

Answer 4

A torch.Size object is a subclass of tuple, and inherits its usual properties e.g. it can be indexed:

v = torch.tensor([[1,2], [3,4]])
v.shape[0]
>>> 2

Note its entries are already of type int.

If you really want a list though, just use the list constructor as with any other iterable:

list(v.shape)

Answered By: iacob

PyTorch: How to get the shape of a Tensor as a list of int

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