class torch.nn.Unflatten(dim, unflattened_size) [source]
 
Unflattens a tensor dim expanding it to a desired shape. For use with Sequential.  
dim specifies the dimension of the input tensor to be unflattened, and it can be either int or str when Tensor or NamedTensor is used, respectively. 
unflattened_size is the new shape of the unflattened dimension of the tensor and it can be a tuple of ints or a list of ints or torch.Size for Tensor input; a NamedShape (tuple of (name, size) tuples) for NamedTensor input.   Shape:

 Input: (N,∗dims)(N, *dims) 
 Output: (N,Cout,Hout,Wout)(N, C_{\text{out}}, H_{\text{out}}, W_{\text{out}}) 
     Parameters 
 
dim (Union[int, str]) – Dimension to be unflattened 
unflattened_size (Union[torch.Size, Tuple, List, NamedShape]) – New shape of the unflattened dimension    Examples >>> input = torch.randn(2, 50)
>>> # With tuple of ints
>>> m = nn.Sequential(
>>>     nn.Linear(50, 50),
>>>     nn.Unflatten(1, (2, 5, 5))
>>> )
>>> output = m(input)
>>> output.size()
torch.Size([2, 2, 5, 5])
>>> # With torch.Size
>>> m = nn.Sequential(
>>>     nn.Linear(50, 50),
>>>     nn.Unflatten(1, torch.Size([2, 5, 5]))
>>> )
>>> output = m(input)
>>> output.size()
torch.Size([2, 2, 5, 5])
>>> # With namedshape (tuple of tuples)
>>> input = torch.randn(2, 50, names=('N', 'features'))
>>> unflatten = nn.Unflatten('features', (('C', 2), ('H', 5), ('W', 5)))
>>> output = unflatten(input)
>>> output.size()
torch.Size([2, 2, 5, 5])
  
add_module(name, module)  
Adds a child module to the current module. The module can be accessed as an attribute using the given name.  Parameters 
 
name (string) – name of the child module. The child module can be accessed from this module using the given name 
module (Module) – child module to be added to the module.    
  
apply(fn)  
Applies fn recursively to every submodule (as returned by .children()) as well as self. Typical use includes initializing the parameters of a model (see also torch.nn.init).  Parameters 
fn (Module -> None) – function to be applied to each submodule  Returns 
self  Return type 
Module   Example: >>> @torch.no_grad()
>>> def init_weights(m):
>>>     print(m)
>>>     if type(m) == nn.Linear:
>>>         m.weight.fill_(1.0)
>>>         print(m.weight)
>>> net = nn.Sequential(nn.Linear(2, 2), nn.Linear(2, 2))
>>> net.apply(init_weights)
Linear(in_features=2, out_features=2, bias=True)
Parameter containing:
tensor([[ 1.,  1.],
        [ 1.,  1.]])
Linear(in_features=2, out_features=2, bias=True)
Parameter containing:
tensor([[ 1.,  1.],
        [ 1.,  1.]])
Sequential(
  (0): Linear(in_features=2, out_features=2, bias=True)
  (1): Linear(in_features=2, out_features=2, bias=True)
)
Sequential(
  (0): Linear(in_features=2, out_features=2, bias=True)
  (1): Linear(in_features=2, out_features=2, bias=True)
)
 
  
bfloat16()  
Casts all floating point parameters and buffers to bfloat16 datatype.  Returns 
self  Return type 
Module   
  
buffers(recurse=True)  
Returns an iterator over module buffers.  Parameters 
recurse (bool) – if True, then yields buffers of this module and all submodules. Otherwise, yields only buffers that are direct members of this module.  Yields 
torch.Tensor – module buffer   Example: >>> for buf in model.buffers():
>>>     print(type(buf), buf.size())
<class 'torch.Tensor'> (20L,)
<class 'torch.Tensor'> (20L, 1L, 5L, 5L)
 
  
children()  
Returns an iterator over immediate children modules.  Yields 
Module – a child module   
  
cpu()  
Moves all model parameters and buffers to the CPU.  Returns 
self  Return type 
Module   
  
cuda(device=None)  
Moves all model parameters and buffers to the GPU. This also makes associated parameters and buffers different objects. So it should be called before constructing optimizer if the module will live on GPU while being optimized.  Parameters 
device (int, optional) – if specified, all parameters will be copied to that device  Returns 
self  Return type 
Module   
  
double()  
Casts all floating point parameters and buffers to double datatype.  Returns 
self  Return type 
Module   
  
eval()  
Sets the module in evaluation mode. This has any effect only on certain modules. See documentations of particular modules for details of their behaviors in training/evaluation mode, if they are affected, e.g. Dropout, BatchNorm, etc. This is equivalent with self.train(False).  Returns 
self  Return type 
Module   
  
float()  
Casts all floating point parameters and buffers to float datatype.  Returns 
self  Return type 
Module   
  
half()  
Casts all floating point parameters and buffers to half datatype.  Returns 
self  Return type 
Module   
  
load_state_dict(state_dict, strict=True)  
Copies parameters and buffers from state_dict into this module and its descendants. If strict is True, then the keys of state_dict must exactly match the keys returned by this module’s state_dict() function.  Parameters 
 
state_dict (dict) – a dict containing parameters and persistent buffers. 
strict (bool, optional) – whether to strictly enforce that the keys in state_dict match the keys returned by this module’s state_dict() function. Default: True
   Returns 
 
missing_keys is a list of str containing the missing keys 
unexpected_keys is a list of str containing the unexpected keys   Return type 
NamedTuple with missing_keys and unexpected_keys fields   
  
modules()  
Returns an iterator over all modules in the network.  Yields 
Module – a module in the network    Note Duplicate modules are returned only once. In the following example, l will be returned only once.  Example: >>> l = nn.Linear(2, 2)
>>> net = nn.Sequential(l, l)
>>> for idx, m in enumerate(net.modules()):
        print(idx, '->', m)

0 -> Sequential(
  (0): Linear(in_features=2, out_features=2, bias=True)
  (1): Linear(in_features=2, out_features=2, bias=True)
)
1 -> Linear(in_features=2, out_features=2, bias=True)
 
  
named_buffers(prefix='', recurse=True)  
Returns an iterator over module buffers, yielding both the name of the buffer as well as the buffer itself.  Parameters 
 
prefix (str) – prefix to prepend to all buffer names. 
recurse (bool) – if True, then yields buffers of this module and all submodules. Otherwise, yields only buffers that are direct members of this module.   Yields 
(string, torch.Tensor) – Tuple containing the name and buffer   Example: >>> for name, buf in self.named_buffers():
>>>    if name in ['running_var']:
>>>        print(buf.size())
 
  
named_children()  
Returns an iterator over immediate children modules, yielding both the name of the module as well as the module itself.  Yields 
(string, Module) – Tuple containing a name and child module   Example: >>> for name, module in model.named_children():
>>>     if name in ['conv4', 'conv5']:
>>>         print(module)
 
  
named_modules(memo=None, prefix='')  
Returns an iterator over all modules in the network, yielding both the name of the module as well as the module itself.  Yields 
(string, Module) – Tuple of name and module    Note Duplicate modules are returned only once. In the following example, l will be returned only once.  Example: >>> l = nn.Linear(2, 2)
>>> net = nn.Sequential(l, l)
>>> for idx, m in enumerate(net.named_modules()):
        print(idx, '->', m)

0 -> ('', Sequential(
  (0): Linear(in_features=2, out_features=2, bias=True)
  (1): Linear(in_features=2, out_features=2, bias=True)
))
1 -> ('0', Linear(in_features=2, out_features=2, bias=True))
 
  
named_parameters(prefix='', recurse=True)  
Returns an iterator over module parameters, yielding both the name of the parameter as well as the parameter itself.  Parameters 
 
prefix (str) – prefix to prepend to all parameter names. 
recurse (bool) – if True, then yields parameters of this module and all submodules. Otherwise, yields only parameters that are direct members of this module.   Yields 
(string, Parameter) – Tuple containing the name and parameter   Example: >>> for name, param in self.named_parameters():
>>>    if name in ['bias']:
>>>        print(param.size())
 
  
parameters(recurse=True)  
Returns an iterator over module parameters. This is typically passed to an optimizer.  Parameters 
recurse (bool) – if True, then yields parameters of this module and all submodules. Otherwise, yields only parameters that are direct members of this module.  Yields 
Parameter – module parameter   Example: >>> for param in model.parameters():
>>>     print(type(param), param.size())
<class 'torch.Tensor'> (20L,)
<class 'torch.Tensor'> (20L, 1L, 5L, 5L)
 
  
register_backward_hook(hook)  
Registers a backward hook on the module. This function is deprecated in favor of nn.Module.register_full_backward_hook() and the behavior of this function will change in future versions.  Returns 
a handle that can be used to remove the added hook by calling handle.remove()  Return type 
torch.utils.hooks.RemovableHandle   
  
register_buffer(name, tensor, persistent=True)  
Adds a buffer to the module. This is typically used to register a buffer that should not to be considered a model parameter. For example, BatchNorm’s running_mean is not a parameter, but is part of the module’s state. Buffers, by default, are persistent and will be saved alongside parameters. This behavior can be changed by setting persistent to False. The only difference between a persistent buffer and a non-persistent buffer is that the latter will not be a part of this module’s state_dict. Buffers can be accessed as attributes using given names.  Parameters 
 
name (string) – name of the buffer. The buffer can be accessed from this module using the given name 
tensor (Tensor) – buffer to be registered. 
persistent (bool) – whether the buffer is part of this module’s state_dict.    Example: >>> self.register_buffer('running_mean', torch.zeros(num_features))
 
  
register_forward_hook(hook)  
Registers a forward hook on the module. The hook will be called every time after forward() has computed an output. It should have the following signature: hook(module, input, output) -> None or modified output
 The input contains only the positional arguments given to the module. Keyword arguments won’t be passed to the hooks and only to the forward. The hook can modify the output. It can modify the input inplace but it will not have effect on forward since this is called after forward() is called.  Returns 
a handle that can be used to remove the added hook by calling handle.remove()  Return type 
torch.utils.hooks.RemovableHandle   
  
register_forward_pre_hook(hook)  
Registers a forward pre-hook on the module. The hook will be called every time before forward() is invoked. It should have the following signature: hook(module, input) -> None or modified input
 The input contains only the positional arguments given to the module. Keyword arguments won’t be passed to the hooks and only to the forward. The hook can modify the input. User can either return a tuple or a single modified value in the hook. We will wrap the value into a tuple if a single value is returned(unless that value is already a tuple).  Returns 
a handle that can be used to remove the added hook by calling handle.remove()  Return type 
torch.utils.hooks.RemovableHandle   
  
register_full_backward_hook(hook)  
Registers a backward hook on the module. The hook will be called every time the gradients with respect to module inputs are computed. The hook should have the following signature: hook(module, grad_input, grad_output) -> tuple(Tensor) or None
 The grad_input and grad_output are tuples that contain the gradients with respect to the inputs and outputs respectively. The hook should not modify its arguments, but it can optionally return a new gradient with respect to the input that will be used in place of grad_input in subsequent computations. grad_input will only correspond to the inputs given as positional arguments and all kwarg arguments are ignored. Entries in grad_input and grad_output will be None for all non-Tensor arguments.  Warning Modifying inputs or outputs inplace is not allowed when using backward hooks and will raise an error.   Returns 
a handle that can be used to remove the added hook by calling handle.remove()  Return type 
torch.utils.hooks.RemovableHandle   
  
register_parameter(name, param)  
Adds a parameter to the module. The parameter can be accessed as an attribute using given name.  Parameters 
 
name (string) – name of the parameter. The parameter can be accessed from this module using the given name 
param (Parameter) – parameter to be added to the module.    
  
requires_grad_(requires_grad=True)  
Change if autograd should record operations on parameters in this module. This method sets the parameters’ requires_grad attributes in-place. This method is helpful for freezing part of the module for finetuning or training parts of a model individually (e.g., GAN training).  Parameters 
requires_grad (bool) – whether autograd should record operations on parameters in this module. Default: True.  Returns 
self  Return type 
Module   
  
state_dict(destination=None, prefix='', keep_vars=False)  
Returns a dictionary containing a whole state of the module. Both parameters and persistent buffers (e.g. running averages) are included. Keys are corresponding parameter and buffer names.  Returns 
a dictionary containing a whole state of the module  Return type 
dict   Example: >>> module.state_dict().keys()
['bias', 'weight']
 
  
to(*args, **kwargs)  
Moves and/or casts the parameters and buffers. This can be called as  
to(device=None, dtype=None, non_blocking=False) 
  
to(dtype, non_blocking=False) 
  
to(tensor, non_blocking=False) 
  
to(memory_format=torch.channels_last) 
 Its signature is similar to torch.Tensor.to(), but only accepts floating point or complex dtype`s. In addition, this method will
only cast the floating point or complex parameters and buffers to :attr:`dtype (if given). The integral parameters and buffers will be moved device, if that is given, but with dtypes unchanged. When non_blocking is set, it tries to convert/move asynchronously with respect to the host if possible, e.g., moving CPU Tensors with pinned memory to CUDA devices. See below for examples.  Note This method modifies the module in-place.   Parameters 
 
device (torch.device) – the desired device of the parameters and buffers in this module 
dtype (torch.dtype) – the desired floating point or complex dtype of the parameters and buffers in this module 
tensor (torch.Tensor) – Tensor whose dtype and device are the desired dtype and device for all parameters and buffers in this module 
memory_format (torch.memory_format) – the desired memory format for 4D parameters and buffers in this module (keyword only argument)   Returns 
self  Return type 
Module   Examples: >>> linear = nn.Linear(2, 2)
>>> linear.weight
Parameter containing:
tensor([[ 0.1913, -0.3420],
        [-0.5113, -0.2325]])
>>> linear.to(torch.double)
Linear(in_features=2, out_features=2, bias=True)
>>> linear.weight
Parameter containing:
tensor([[ 0.1913, -0.3420],
        [-0.5113, -0.2325]], dtype=torch.float64)
>>> gpu1 = torch.device("cuda:1")
>>> linear.to(gpu1, dtype=torch.half, non_blocking=True)
Linear(in_features=2, out_features=2, bias=True)
>>> linear.weight
Parameter containing:
tensor([[ 0.1914, -0.3420],
        [-0.5112, -0.2324]], dtype=torch.float16, device='cuda:1')
>>> cpu = torch.device("cpu")
>>> linear.to(cpu)
Linear(in_features=2, out_features=2, bias=True)
>>> linear.weight
Parameter containing:
tensor([[ 0.1914, -0.3420],
        [-0.5112, -0.2324]], dtype=torch.float16)

>>> linear = nn.Linear(2, 2, bias=None).to(torch.cdouble)
>>> linear.weight
Parameter containing:
tensor([[ 0.3741+0.j,  0.2382+0.j],
        [ 0.5593+0.j, -0.4443+0.j]], dtype=torch.complex128)
>>> linear(torch.ones(3, 2, dtype=torch.cdouble))
tensor([[0.6122+0.j, 0.1150+0.j],
        [0.6122+0.j, 0.1150+0.j],
        [0.6122+0.j, 0.1150+0.j]], dtype=torch.complex128)
 
  
train(mode=True)  
Sets the module in training mode. This has any effect only on certain modules. See documentations of particular modules for details of their behaviors in training/evaluation mode, if they are affected, e.g. Dropout, BatchNorm, etc.  Parameters 
mode (bool) – whether to set training mode (True) or evaluation mode (False). Default: True.  Returns 
self  Return type 
Module   
  
type(dst_type)  
Casts all parameters and buffers to dst_type.  Parameters 
dst_type (type or string) – the desired type  Returns 
self  Return type 
Module   
  
xpu(device=None)  
Moves all model parameters and buffers to the XPU. This also makes associated parameters and buffers different objects. So it should be called before constructing optimizer if the module will live on XPU while being optimized.  Parameters 
device (int, optional) – if specified, all parameters will be copied to that device  Returns 
self  Return type 
Module   
  
zero_grad(set_to_none=False)  
Sets gradients of all model parameters to zero. See similar function under torch.optim.Optimizer for more context.  Parameters 
set_to_none (bool) – instead of setting to zero, set the grads to None. See torch.optim.Optimizer.zero_grad() for details.