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社区首页 >专栏 >tf.Tensor

tf.Tensor

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狼啸风云
发布2022-06-06 07:58:43
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发布2022-06-06 07:58:43
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文章被收录于专栏:计算机视觉理论及其实现

目录

Class Tensor

__init__

Properties

device

dtype

graph

name

op

shape

Methods

1、__abs__

2、__add__

3、__and__

4、__bool__

5、__div__

6、__eq__

7、__floordiv__

8、__ge__

9、__getitem__

10、__gt__

10、__invert__

11、__iter__

12、__le__

13、__len__

14、__lt__

15、__matmul__

16、__mod__

17、__mul__

18、__ne__

19、__neg__

20、__nonzero__

21、__or__

22、__pow__

23、__radd__

24、__rand__

25、__rdiv__

26、__rfloordiv__

27、__rmatmul__

28、__rmod__

29、__rmul__

30、__ror__

31、__rpow__

32、__rsub__

33、__rtruediv__

34、__rxor__

35、__sub__

36、__truediv__

37、__xor__

38、consumers

39、eval

40、experimental_ref

41、get_shape

42、set_shape



Class Tensor

Represents one of the outputs of an Operation.

Aliases:

A Tensor is a symbolic handle to one of the outputs of an Operation. It does not hold the values of that operation's output, but instead provides a means of computing those values in a TensorFlow tf.compat.v1.Session.

This class has two primary purposes:

  1. A Tensor can be passed as an input to another Operation. This builds a dataflow connection between operations, which enables TensorFlow to execute an entire Graph that represents a large, multi-step computation.
  2. After the graph has been launched in a session, the value of the Tensor can be computed by passing it to tf.Session.run. t.eval() is a shortcut for calling tf.compat.v1.get_default_session().run(t).

In the following example, c, d, and e are symbolic Tensor objects, whereas result is a numpy array that stores a concrete value:

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# Build a dataflow graph.
c = tf.constant([[1.0, 2.0], [3.0, 4.0]])
d = tf.constant([[1.0, 1.0], [0.0, 1.0]])
e = tf.matmul(c, d)

# Construct a `Session` to execute the graph.
sess = tf.compat.v1.Session()

# Execute the graph and store the value that `e` represents in `result`.
result = sess.run(e)

__init__

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__init__(
    op,
    value_index,
    dtype
)

Creates a new Tensor.

Args:

  • op: An Operation. Operation that computes this tensor.
  • value_index: An int. Index of the operation's endpoint that produces this tensor.
  • dtype: A DType. Type of elements stored in this tensor.

Raises:

  • TypeError: If the op is not an Operation.

Properties

device

The name of the device on which this tensor will be produced, or None.

dtype

The DType of elements in this tensor.

graph

The Graph that contains this tensor.

name

The string name of this tensor.

op

The Operation that produces this tensor as an output.

shape

Returns the TensorShape that represents the shape of this tensor.

The shape is computed using shape inference functions that are registered in the Op for each Operation. See tf.TensorShape for more details of what a shape represents.

The inferred shape of a tensor is used to provide shape information without having to launch the graph in a session. This can be used for debugging, and providing early error messages. For example:

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c = tf.constant([[1.0, 2.0, 3.0], [4.0, 5.0, 6.0]])

print(c.shape)
==> TensorShape([Dimension(2), Dimension(3)])

d = tf.constant([[1.0, 0.0], [0.0, 1.0], [1.0, 0.0], [0.0, 1.0]])

print(d.shape)
==> TensorShape([Dimension(4), Dimension(2)])

# Raises a ValueError, because `c` and `d` do not have compatible
# inner dimensions.
e = tf.matmul(c, d)

f = tf.matmul(c, d, transpose_a=True, transpose_b=True)

print(f.shape)
==> TensorShape([Dimension(3), Dimension(4)])

In some cases, the inferred shape may have unknown dimensions. If the caller has additional information about the values of these dimensions, Tensor.set_shape() can be used to augment the inferred shape.

Returns:

A TensorShape representing the shape of this tensor.

value_index

The index of this tensor in the outputs of its Operation.

Methods

1、__abs__

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__abs__(
    x,
    name=None
)

Computes the absolute value of a tensor.Given a tensor of integer or floating-point values, this operation returns a tensor of the same type, where each element contains the absolute value of the corresponding element in the input.Given a tensor x of complex numbers, this operation returns a tensor of type float32 or float64 that is the absolute value of each element in x. All elements in x must be complex numbers of the form. The absolute value is computed as. For example:

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x = tf.constant([[-2.25 + 4.75j], [-3.25 + 5.75j]])
tf.abs(x)  # [5.25594902, 6.60492229]

Args:

  • x: A Tensor or SparseTensor of type float16, float32, float64, int32, int64, complex64 or complex128.
  • name: A name for the operation (optional).

Returns:

  • A Tensor or SparseTensor the same size, type, and sparsity as x with absolute values. Note, for complex64 or complex128 input, the returned Tensor will be of type float32 or float64, respectively.

If x is a SparseTensor, returns SparseTensor(x.indices, tf.math.abs(x.values, ...), x.dense_shape)

2、__add__

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__add__(
    x,
    y
)

Dispatches to add for strings and add_v2 for all other types.

3、__and__

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__and__(
    x,
    y
)

Returns the truth value of x AND y element-wise.

NOTE: math.logical_and supports broadcasting. More about broadcasting here

Args:

  • x: A Tensor of type bool.
  • y: A Tensor of type bool.
  • name: A name for the operation (optional).

Returns:

  • A Tensor of type bool.

4、__bool__

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__bool__()

Dummy method to prevent a tensor from being used as a Python bool.

This overload raises a TypeError when the user inadvertently treats a Tensor as a boolean (most commonly in an if or while statement), in code that was not converted by AutoGraph. For example:

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if tf.constant(True):  # Will raise.
  # ...

if tf.constant(5) < tf.constant(7):  # Will raise.
  # ...

Raises:

  • TypeError.

5、__div__

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__div__(
    x,
    y
)

Divide two values using Python 2 semantics.

Used for Tensor.div.

Args:

  • x: Tensor numerator of real numeric type.
  • y: Tensor denominator of real numeric type.
  • name: A name for the operation (optional).

Returns:

  • x / y returns the quotient of x and y.

6、__eq__

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__eq__(other)

Compares two tensors element-wise for equality.

7、__floordiv__

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__floordiv__(
    x,
    y
)

Divides x / y elementwise, rounding toward the most negative integer.

The same as tf.compat.v1.div(x,y) for integers, but uses tf.floor(tf.compat.v1.div(x,y)) for floating point arguments so that the result is always an integer (though possibly an integer represented as floating point). This op is generated by x // y floor division in Python 3 and in Python 2.7 with from __future__ import division.

x and y must have the same type, and the result will have the same type as well.

Args:

  • x: Tensor numerator of real numeric type.
  • y: Tensor denominator of real numeric type.
  • name: A name for the operation (optional).

Returns:

  • x / y rounded down.

Raises:

  • TypeError: If the inputs are complex.

8、__ge__

Defined in generated file: python/ops/gen_math_ops.py

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__ge__(
    x,
    y,
    name=None
)

Returns the truth value of (x >= y) element-wise.

NOTE: math.greater_equal supports broadcasting. More about broadcasting here

Args:

  • x: A Tensor. Must be one of the following types: float32, float64, int32, uint8, int16, int8, int64, bfloat16, uint16, half, uint32, uint64.
  • y: A Tensor. Must have the same type as x.
  • name: A name for the operation (optional).

Returns:

  • A Tensor of type bool.

9、__getitem__

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__getitem__(
    tensor,
    slice_spec,
    var=None
)

Overload for Tensor.getitem.

This operation extracts the specified region from the tensor. The notation is similar to NumPy with the restriction that currently only support basic indexing. That means that using a non-scalar tensor as input is not currently allowed.

Some useful examples:

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# Strip leading and trailing 2 elements
foo = tf.constant([1,2,3,4,5,6])
print(foo[2:-2].eval())  # => [3,4]

# Skip every other row and reverse the order of the columns
foo = tf.constant([[1,2,3], [4,5,6], [7,8,9]])
print(foo[::2,::-1].eval())  # => [[3,2,1], [9,8,7]]

# Use scalar tensors as indices on both dimensions
print(foo[tf.constant(0), tf.constant(2)].eval())  # => 3

# Insert another dimension
foo = tf.constant([[1,2,3], [4,5,6], [7,8,9]])
print(foo[tf.newaxis, :, :].eval()) # => [[[1,2,3], [4,5,6], [7,8,9]]]
print(foo[:, tf.newaxis, :].eval()) # => [[[1,2,3]], [[4,5,6]], [[7,8,9]]]
print(foo[:, :, tf.newaxis].eval()) # => [[[1],[2],[3]], [[4],[5],[6]],
[[7],[8],[9]]]

# Ellipses (3 equivalent operations)
foo = tf.constant([[1,2,3], [4,5,6], [7,8,9]])
print(foo[tf.newaxis, :, :].eval())  # => [[[1,2,3], [4,5,6], [7,8,9]]]
print(foo[tf.newaxis, ...].eval())  # => [[[1,2,3], [4,5,6], [7,8,9]]]
print(foo[tf.newaxis].eval())  # => [[[1,2,3], [4,5,6], [7,8,9]]]

# Masks
foo = tf.constant([[1,2,3], [4,5,6], [7,8,9]])
print(foo[foo > 2].eval())  # => [3, 4, 5, 6, 7, 8, 9]

Notes:

  • tf.newaxis is None as in NumPy.
  • An implicit ellipsis is placed at the end of the slice_spec
  • NumPy advanced indexing is currently not supported.

Args:

  • tensor: An ops.Tensor object.
  • slice_spec: The arguments to Tensor.getitem.
  • var: In the case of variable slice assignment, the Variable object to slice (i.e. tensor is the read-only view of this variable).

Returns:

  • The appropriate slice of "tensor", based on "slice_spec".

Raises:

  • ValueError: If a slice range is negative size.
  • TypeError: If the slice indices aren't int, slice, ellipsis, tf.newaxis or scalar int32/int64 tensors.

10、__gt__

Defined in generated file: python/ops/gen_math_ops.py

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__gt__(
    x,
    y,
    name=None
)

Returns the truth value of (x > y) element-wise.

NOTE: math.greater supports broadcasting. More about broadcasting here

Args:

  • x: A Tensor. Must be one of the following types: float32, float64, int32, uint8, int16, int8, int64, bfloat16, uint16, half, uint32, uint64.
  • y: A Tensor. Must have the same type as x.
  • name: A name for the operation (optional).

Returns:

  • A Tensor of type bool.

10、__invert__

Defined in generated file: python/ops/gen_math_ops.py

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__invert__(
    x,
    name=None
)

Returns the truth value of NOT x element-wise.

Args:

  • x: A Tensor of type bool.
  • name: A name for the operation (optional).

Returns:

  • A Tensor of type bool.

11、__iter__

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__iter__()

12、__le__

Defined in generated file: python/ops/gen_math_ops.py

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__le__(
    x,
    y,
    name=None
)

Returns the truth value of (x <= y) element-wise.

NOTE: math.less_equal supports broadcasting. More about broadcasting here

Args:

  • x: A Tensor. Must be one of the following types: float32, float64, int32, uint8, int16, int8, int64, bfloat16, uint16, half, uint32, uint64.
  • y: A Tensor. Must have the same type as x.
  • name: A name for the operation (optional).

Returns:

  • A Tensor of type bool.

13、__len__

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__len__()

14、__lt__

Defined in generated file: python/ops/gen_math_ops.py

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__lt__(
    x,
    y,
    name=None
)

Returns the truth value of (x < y) element-wise.

NOTE: math.less supports broadcasting. More about broadcasting here

Args:

  • x: A Tensor. Must be one of the following types: float32, float64, int32, uint8, int16, int8, int64, bfloat16, uint16, half, uint32, uint64.
  • y: A Tensor. Must have the same type as x.
  • name: A name for the operation (optional).

Returns:

  • A Tensor of type bool.

15、__matmul__

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__matmul__(
    x,
    y
)

Multiplies matrix a by matrix b, producing a * b.

The inputs must, following any transpositions, be tensors of rank >= 2 where the inner 2 dimensions specify valid matrix multiplication arguments, and any further outer dimensions match.

Both matrices must be of the same type. The supported types are: float16, float32, float64, int32, complex64, complex128.

Either matrix can be transposed or adjointed (conjugated and transposed) on the fly by setting one of the corresponding flag to True. These are False by default.

If one or both of the matrices contain a lot of zeros, a more efficient multiplication algorithm can be used by setting the corresponding a_is_sparse or b_is_sparse flag to True. These are False by default. This optimization is only available for plain matrices (rank-2 tensors) with datatypes bfloat16 or float32.

For example:

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# 2-D tensor `a`
# [[1, 2, 3],
#  [4, 5, 6]]
a = tf.constant([1, 2, 3, 4, 5, 6], shape=[2, 3])

# 2-D tensor `b`
# [[ 7,  8],
#  [ 9, 10],
#  [11, 12]]
b = tf.constant([7, 8, 9, 10, 11, 12], shape=[3, 2])

# `a` * `b`
# [[ 58,  64],
#  [139, 154]]
c = tf.matmul(a, b)


# 3-D tensor `a`
# [[[ 1,  2,  3],
#   [ 4,  5,  6]],
#  [[ 7,  8,  9],
#   [10, 11, 12]]]
a = tf.constant(np.arange(1, 13, dtype=np.int32),
                shape=[2, 2, 3])

# 3-D tensor `b`
# [[[13, 14],
#   [15, 16],
#   [17, 18]],
#  [[19, 20],
#   [21, 22],
#   [23, 24]]]
b = tf.constant(np.arange(13, 25, dtype=np.int32),
                shape=[2, 3, 2])

# `a` * `b`
# [[[ 94, 100],
#   [229, 244]],
#  [[508, 532],
#   [697, 730]]]
c = tf.matmul(a, b)

# Since python >= 3.5 the @ operator is supported (see PEP 465).
# In TensorFlow, it simply calls the `tf.matmul()` function, so the
# following lines are equivalent:
d = a @ b @ [[10.], [11.]]
d = tf.matmul(tf.matmul(a, b), [[10.], [11.]])

Args:

  • a: Tensor of type float16, float32, float64, int32, complex64, complex128 and rank > 1.
  • b: Tensor with same type and rank as a.
  • transpose_a: If True, a is transposed before multiplication.
  • transpose_b: If True, b is transposed before multiplication.
  • adjoint_a: If True, a is conjugated and transposed before multiplication.
  • adjoint_b: If True, b is conjugated and transposed before multiplication.
  • a_is_sparse: If True, a is treated as a sparse matrix.
  • b_is_sparse: If True, b is treated as a sparse matrix.
  • name: Name for the operation (optional).

Returns:

  • A Tensor of the same type as a and b where each inner-most matrix is the product of the corresponding matrices in a and b, e.g. if all transpose or adjoint attributes are False:output[..., i, j] = sum_k (a[..., i, k] * b[..., k, j]), for all indices i, j.Note: This is matrix product, not element-wise product.

Raises:

  • ValueError: If transpose_a and adjoint_a, or transpose_b and adjoint_b are both set to True.

16、__mod__

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__mod__(
    x,
    y
)

Returns element-wise remainder of division. When x < 0 xor y < 0 is

true, this follows Python semantics in that the result here is consistent with a flooring divide. E.g. floor(x / y) * y + mod(x, y) = x.

NOTE: math.floormod supports broadcasting. More about broadcasting here

Args:

  • x: A Tensor. Must be one of the following types: int32, int64, bfloat16, half, float32, float64.
  • y: A Tensor. Must have the same type as x.
  • name: A name for the operation (optional).

Returns:

  • A Tensor. Has the same type as x.

17、__mul__

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__mul__(
    x,
    y
)

Dispatches cwise mul for "DenseDense" and "DenseSparse".

18、__ne__

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__ne__(other)

Compares two tensors element-wise for equality.

19、__neg__

Defined in generated file: python/ops/gen_math_ops.py

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__neg__(
    x,
    name=None
)

Computes numerical negative value element-wise.

I.e.,

Args:

  • x: A Tensor. Must be one of the following types: bfloat16, half, float32, float64, int32, int64, complex64, complex128.
  • name: A name for the operation (optional).

Returns:

  • A Tensor. Has the same type as x.If x is a SparseTensor, returns SparseTensor(x.indices, tf.math.negative(x.values, ...), x.dense_shape)

20、__nonzero__

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__nonzero__()

Dummy method to prevent a tensor from being used as a Python bool.

This is the Python 2.x counterpart to __bool__() above.

Raises:

  • TypeError.

21、__or__

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__or__(
    x,
    y
)

Returns the truth value of x OR y element-wise.

NOTE: math.logical_or supports broadcasting. More about broadcasting here

Args:

  • x: A Tensor of type bool.
  • y: A Tensor of type bool.
  • name: A name for the operation (optional).

Returns:

  • A Tensor of type bool.

22、__pow__

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__pow__(
    x,
    y
)

Computes the power of one value to another.

Given a tensor x and a tensor y, this operation computes

for corresponding elements in x and y. For example:

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x = tf.constant([[2, 2], [3, 3]])
y = tf.constant([[8, 16], [2, 3]])
tf.pow(x, y)  # [[256, 65536], [9, 27]]

Args:

  • x: A Tensor of type float16, float32, float64, int32, int64, complex64, or complex128.
  • y: A Tensor of type float16, float32, float64, int32, int64, complex64, or complex128.
  • name: A name for the operation (optional).

Returns:

  • A Tensor.

23、__radd__

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__radd__(
    y,
    x
)

Dispatches to add for strings and add_v2 for all other types.

24、__rand__

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__rand__(
    y,
    x
)

Returns the truth value of x AND y element-wise.

NOTE: math.logical_and supports broadcasting. More about broadcasting here

Args:

  • x: A Tensor of type bool.
  • y: A Tensor of type bool.
  • name: A name for the operation (optional).

Returns:

  • A Tensor of type bool.

25、__rdiv__

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__rdiv__(
    y,
    x
)

Divide two values using Python 2 semantics.

Used for Tensor.div.

Args:

  • x: Tensor numerator of real numeric type.
  • y: Tensor denominator of real numeric type.
  • name: A name for the operation (optional).

Returns:

  • x / y returns the quotient of x and y.

26、__rfloordiv__

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__rfloordiv__(
    y,
    x
)

Divides x / y elementwise, rounding toward the most negative integer.

The same as tf.compat.v1.div(x,y) for integers, but uses tf.floor(tf.compat.v1.div(x,y)) for floating point arguments so that the result is always an integer (though possibly an integer represented as floating point). This op is generated by x // y floor division in Python 3 and in Python 2.7 with from __future__ import division.

x and y must have the same type, and the result will have the same type as well.

Args:

  • x: Tensor numerator of real numeric type.
  • y: Tensor denominator of real numeric type.
  • name: A name for the operation (optional).

Returns:

  • x / y rounded down.

Raises:

  • TypeError: If the inputs are complex.

27、__rmatmul__

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__rmatmul__(
    y,
    x
)

Multiplies matrix a by matrix b, producing a * b.

The inputs must, following any transpositions, be tensors of rank >= 2 where the inner 2 dimensions specify valid matrix multiplication arguments, and any further outer dimensions match.

Both matrices must be of the same type. The supported types are: float16, float32, float64, int32, complex64, complex128.

Either matrix can be transposed or adjointed (conjugated and transposed) on the fly by setting one of the corresponding flag to True. These are False by default.

If one or both of the matrices contain a lot of zeros, a more efficient multiplication algorithm can be used by setting the corresponding a_is_sparse or b_is_sparse flag to True. These are False by default. This optimization is only available for plain matrices (rank-2 tensors) with datatypes bfloat16 or float32.

For example:

Args:

  • a: Tensor of type float16, float32, float64, int32, complex64, complex128 and rank > 1.
  • b: Tensor with same type and rank as a.
  • transpose_a: If True, a is transposed before multiplication.
  • transpose_b: If True, b is transposed before multiplication.
  • adjoint_a: If True, a is conjugated and transposed before multiplication.
  • adjoint_b: If True, b is conjugated and transposed before multiplication.
  • a_is_sparse: If True, a is treated as a sparse matrix.
  • b_is_sparse: If True, b is treated as a sparse matrix.
  • name: Name for the operation (optional).

Returns:

  • A Tensor of the same type as a and b where each inner-most matrix is the product of the corresponding matrices in a and b, e.g. if all transpose or adjoint attributes are False:output[..., i, j] = sum_k (a[..., i, k] * b[..., k, j]), for all indices i, j.Note: This is matrix product, not element-wise product.

Raises:

  • ValueError: If transpose_a and adjoint_a, or transpose_b and adjoint_b are both set to True.

28、__rmod__

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__rmod__(
    y,
    x
)

Returns element-wise remainder of division. When x < 0 xor y < 0 is

true, this follows Python semantics in that the result here is consistent with a flooring divide. E.g. floor(x / y) * y + mod(x, y) = x.

NOTE: math.floormod supports broadcasting. More about broadcasting here

Args:

  • x: A Tensor. Must be one of the following types: int32, int64, bfloat16, half, float32, float64.
  • y: A Tensor. Must have the same type as x.
  • name: A name for the operation (optional).

Returns:

  • A Tensor. Has the same type as x.

29、__rmul__

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__rmul__(
    y,
    x
)

Dispatches cwise mul for "DenseDense" and "DenseSparse".

30、__ror__

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__ror__(
    y,
    x
)

Returns the truth value of x OR y element-wise.

NOTE: math.logical_or supports broadcasting. More about broadcasting here

Args:

  • x: A Tensor of type bool.
  • y: A Tensor of type bool.
  • name: A name for the operation (optional).

Returns:

  • A Tensor of type bool.

31、__rpow__

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__rpow__(
    y,
    x
)

Computes the power of one value to another.

Given a tensor x and a tensor y, this operation computes

for corresponding elements in x and y. For example:

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x = tf.constant([[2, 2], [3, 3]])
y = tf.constant([[8, 16], [2, 3]])
tf.pow(x, y)  # [[256, 65536], [9, 27]]

Args:

  • x: A Tensor of type float16, float32, float64, int32, int64, complex64, or complex128.
  • y: A Tensor of type float16, float32, float64, int32, int64, complex64, or complex128.
  • name: A name for the operation (optional).

Returns:

  • A Tensor.

32、__rsub__

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__rsub__(
    y,
    x
)

Returns x - y element-wise.

NOTE: Subtract supports broadcasting. More about broadcasting here

Args:

  • x: A Tensor. Must be one of the following types: bfloat16, half, float32, float64, uint8, int8, uint16, int16, int32, int64, complex64, complex128.
  • y: A Tensor. Must have the same type as x.
  • name: A name for the operation (optional).

Returns:

  • A Tensor. Has the same type as x.

33、__rtruediv__

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代码语言:javascript
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__rtruediv__(
    y,
    x
)

34、__rxor__

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代码语言:javascript
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__rxor__(
    y,
    x
)

Logical XOR function.

x ^ y = (x | y) & ~(x & y)

Inputs are tensor and if the tensors contains more than one element, an element-wise logical XOR is computed.

Usage:

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x = tf.constant([False, False, True, True], dtype = tf.bool)
y = tf.constant([False, True, False, True], dtype = tf.bool)
z = tf.logical_xor(x, y, name="LogicalXor")
#  here z = [False  True  True False]

Args:

  • x: A Tensor type bool.
  • y: A Tensor of type bool.

Returns:

  • A Tensor of type bool with the same size as that of x or y.

35、__sub__

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代码语言:javascript
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__sub__(
    x,
    y
)

Returns x - y element-wise.

NOTE: Subtract supports broadcasting. More about broadcasting here

Args:

  • x: A Tensor. Must be one of the following types: bfloat16, half, float32, float64, uint8, int8, uint16, int16, int32, int64, complex64, complex128.
  • y: A Tensor. Must have the same type as x.
  • name: A name for the operation (optional).

Returns:

  • A Tensor. Has the same type as x.

36、__truediv__

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代码语言:javascript
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__truediv__(
    x,
    y
)

37、__xor__

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代码语言:javascript
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__xor__(
    x,
    y
)

Logical XOR function.

x ^ y = (x | y) & ~(x & y)

Inputs are tensor and if the tensors contains more than one element, an element-wise logical XOR is computed.

Usage:

代码语言:javascript
复制
x = tf.constant([False, False, True, True], dtype = tf.bool)
y = tf.constant([False, True, False, True], dtype = tf.bool)
z = tf.logical_xor(x, y, name="LogicalXor")
#  here z = [False  True  True False]

Args:

  • x: A Tensor type bool.
  • y: A Tensor of type bool.

Returns:

  • A Tensor of type bool with the same size as that of x or y.

38、consumers

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consumers()

Returns a list of Operations that consume this tensor.

Returns:

A list of Operations.

39、eval

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eval(
    feed_dict=None,
    session=None
)

Evaluates this tensor in a Session.Calling this method will execute all preceding operations that produce the inputs needed for the operation that produces this tensor.

N.B. Before invoking Tensor.eval(), its graph must have been launched in a session, and either a default session must be available, or session must be specified explicitly.

Args:

  • feed_dict: A dictionary that maps Tensor objects to feed values. See tf.Session.run for a description of the valid feed values.
  • session: (Optional.) The Session to be used to evaluate this tensor. If none, the default session will be used.

Returns:

  • A numpy array corresponding to the value of this tensor.

例:

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import tensorflow as tf

a=tf.constant([1.0,2.0],name="a")
b=tf.constant([2.0,3.0],name="b")
c=tf.add(a,b,name="sum")

print(c)

sess=tf.Session()
with sess.as_default():
    print(c.eval())



Output:
--------------------------------------------
Tensor(“sum:0”, shape=(2,), dtype=float32)
[ 3. 5.]
--------------------------------------------

40、experimental_ref

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experimental_ref()

Returns a hashable reference object to this Tensor.

Warning: Experimental API that could be changed or removed.

The primary usecase for this API is to put tensors in a set/dictionary. We can't put tensors in a set/dictionary as tensor.__hash__() is no longer available starting Tensorflow 2.0.

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import tensorflow as tf

x = tf.constant(5)
y = tf.constant(10)
z = tf.constant(10)

# The followings will raise an exception starting 2.0
# TypeError: Tensor is unhashable if Tensor equality is enabled.
tensor_set = {x, y, z}
tensor_dict = {x: 'five', y: 'ten', z: 'ten'}

Instead, we can use tensor.experimental_ref().

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tensor_set = {x.experimental_ref(),
              y.experimental_ref(),
              z.experimental_ref()}

print(x.experimental_ref() in tensor_set)
==> True

tensor_dict = {x.experimental_ref(): 'five',
               y.experimental_ref(): 'ten',
               z.experimental_ref(): 'ten'}

print(tensor_dict[y.experimental_ref()])
==> ten

Also, the reference object provides .deref() function that returns the original Tensor.

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x = tf.constant(5)
print(x.experimental_ref().deref())
==> tf.Tensor(5, shape=(), dtype=int32)

41、get_shape

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get_shape()

Alias of Tensor.shape.

42、set_shape

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set_shape(shape)

Updates the shape of this tensor.

This method can be called multiple times, and will merge the given shape with the current shape of this tensor. It can be used to provide additional information about the shape of this tensor that cannot be inferred from the graph alone. For example, this can be used to provide additional information about the shapes of images:

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_, image_data = tf.compat.v1.TFRecordReader(...).read(...)
image = tf.image.decode_png(image_data, channels=3)

# The height and width dimensions of `image` are data dependent, and
# cannot be computed without executing the op.
print(image.shape)
==> TensorShape([Dimension(None), Dimension(None), Dimension(3)])

# We know that each image in this dataset is 28 x 28 pixels.
image.set_shape([28, 28, 3])
print(image.shape)
==> TensorShape([Dimension(28), Dimension(28), Dimension(3)])

NOTE: This shape is not enforced at runtime. Setting incorrect shapes can result in inconsistencies between the statically-known graph and the runtime value of tensors. For runtime validation of the shape, use tf.ensure_shape instead.

Args:

  • shape: A TensorShape representing the shape of this tensor, a TensorShapeProto, a list, a tuple, or None.

Raises:

  • ValueError: If shape is not compatible with the current shape of this tensor.
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目录
  • Class Tensor
    • __init__
    • Properties
      • device
        • dtype
          • graph
            • name
              • op
                • shape
                • Methods
                  • 1、__abs__
                    • 2、__add__
                      • 3、__and__
                        • 4、__bool__
                          • 5、__div__
                            • 6、__eq__
                              • 7、__floordiv__
                                • 8、__ge__
                                  • 9、__getitem__
                                    • 10、__gt__
                                      • 10、__invert__
                                        • 11、__iter__
                                          • 12、__le__
                                            • 13、__len__
                                              • 14、__lt__
                                                • 15、__matmul__
                                                  • 16、__mod__
                                                    • 17、__mul__
                                                      • 18、__ne__
                                                        • 19、__neg__
                                                          • 20、__nonzero__
                                                            • 21、__or__
                                                              • 22、__pow__
                                                                • 23、__radd__
                                                                  • 24、__rand__
                                                                    • 25、__rdiv__
                                                                      • 26、__rfloordiv__
                                                                        • 27、__rmatmul__
                                                                          • 28、__rmod__
                                                                            • 29、__rmul__
                                                                              • 30、__ror__
                                                                                • 31、__rpow__
                                                                                  • 32、__rsub__
                                                                                    • 33、__rtruediv__
                                                                                      • 34、__rxor__
                                                                                        • 35、__sub__
                                                                                          • 36、__truediv__
                                                                                            • 37、__xor__
                                                                                              • 38、consumers
                                                                                                • 39、eval
                                                                                                  • 40、experimental_ref
                                                                                                    • 41、get_shape
                                                                                                      • 42、set_shape
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