# Tensor attributes

Source: https://www.tensorplay.cn/docs/tensor_attributes.html

A tensor carries metadata alongside its data: a data type, a device, and a shape. This page
covers the two that describe what an element is and where it lives. Shape is described in
[Size](/docs/size.html).

## Data type

A tensor’s data type (dtype) states how each element is stored and what range of values it can
hold. The common dtypes are exposed as constants:

```
import tensorplay as tp

print(tp.float32)   # the 32-bit floating-point dtype
print(tp.int64)     # the 64-bit integer dtype
print(tp.bool)      # a boolean dtype
```

Pass a dtype to a creation function or Tensor to control it:

```
x = tp.tensor([1, 2, 3], dtype=tp.float32)
print(x.dtype)      # tensorplay.float32
```

There are integer, floating-point, and complex dtypes (tensorplay.complex64,
tensorplay.complex128). Operations that mix dtypes promote according to TensorPlay’s
type-promotion rules, so a float32 tensor times an int64 tensor yields a float32 tensor.

| tensorplay.dtype | |
| --- | --- |
| tensorplay.get_default_dtype | Get the current default floating point tensorplay.dtype. |
| tensorplay.set_default_dtype | Sets the default floating point dtype to d. |

## Device

A tensor lives on a device — cpu, or a GPU such as cuda. The device determines where the
data is physically stored and which kernels can run on it:

```
x = tp.tensor([1.0, 2.0])
print(x.device)      # cpu
```

Use .to(device) to move a tensor (and model.to(device) to move a model) to another device.
See the [CUDA](/docs/cuda.html) page for working with accelerators.

| tensorplay.device | |
| --- | --- |
| tensorplay.get_default_device | Gets the default tensorplay.Tensor to be allocated on device |
| tensorplay.set_default_device | Sets the default tensorplay.Tensor to be allocated on device. |

## Defaults

set_default_dtype and set_default_device change the dtype and device used for tensors
created without an explicit one, and get_default_dtype / get_default_device read them back.

## Where to go next

- [Tensors](/docs/tensorplay.html) — the full tensor creation and math API.

- [Type information](/docs/type_info.html) — finfo and iinfo, the per-dtype limits.