numpy.expand_dims — NumPy v2.2 Manual (original) (raw)

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.

Parameters:

aarray_like

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 asaxis == a.ndim, and passing axis < -a.ndim - 1 will be treated as axis == 0. This behavior is deprecated.

Returns:

resultndarray

View of a with the number of dimensions increased.

Examples

import numpy as np 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