ma.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.

axisint or tuple of ints

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


The inverse operation, removing singleton dimensions


Insert, remove, and combine dimensions, and resize existing ones

doc.indexing, atleast_1d, atleast_2d, atleast_3d


>>> x = np.array([1, 2])
>>> x.shape

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
>>> 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

Note that some examples may use None instead of np.newaxis. These are the same objects:

>>> np.newaxis is None