numpy.expand_dims(a, axis)[source]¶Expand the shape of an array.
Insert a new axis that will appear at the axis position in the expanded array shape.
Input array.
Position in the expanded axes where the new axis (or axes) is placed.
Deprecated since version 1.13.0: Passing an axis where axis > a.ndim will be treated as
axis == a.ndim, and passing axis < -a.ndim - 1 will
be treated as axis == 0. This behavior is deprecated.
Changed in version 1.18.0: A tuple of axes is now supported. Out of range axes as
described above are now forbidden and raise an AxisError.
View of a with the number of dimensions increased.
See also
Examples
>>> x = np.array([1, 2])
>>> x.shape
(2,)
The following is equivalent to x[np.newaxis, :] or x[np.newaxis]:
>>> y = np.expand_dims(x, axis=0)
>>> y
array([[1, 2]])
>>> y.shape
(1, 2)
The following is equivalent to x[:, np.newaxis]:
>>> y = np.expand_dims(x, axis=1)
>>> y
array([[1],
[2]])
>>> y.shape
(2, 1)
axis may also be a tuple:
>>> y = np.expand_dims(x, axis=(0, 1))
>>> y
array([[[1, 2]]])
>>> y = np.expand_dims(x, axis=(2, 0))
>>> y
array([[[1],
[2]]])
Note that some examples may use None instead of np.newaxis. These
are the same objects:
>>> np.newaxis is None
True