numpy.expand_dims

此函数通过在指定位置插入新轴来扩展阵列。该功能需要两个参数。

numpy.expand_dims(arr, axis)

这里

序号	参数和描述
1	arr 输入数组
2	axis 插入新轴的位置

例

import numpy as np
x = np.array(([1,2],[3,4]))

print 'Array x:'
print x
print '\n'  
y = np.expand_dims(x, axis = 0)

print 'Array y:'
print y
print '\n'

print 'The shape of X and Y array:'
print x.shape, y.shape
print '\n'  
# insert axis at position 1
y = np.expand_dims(x, axis = 1)

print 'Array Y after inserting axis at position 1:'
print y
print '\n'  

print 'x.ndim and y.ndim:'
print x.ndim,y.ndim
print '\n'  

print 'x.shape and y.shape:'
print x.shape, y.shape

上述方案的输出如下

Array x:
[[1 2]
 [3 4]]

Array y:
[[[1 2]
 [3 4]]]

The shape of X and Y array:
(2, 2) (1, 2, 2)

Array Y after inserting axis at position 1:
[[[1 2]]
 [[3 4]]]

x.ndim and y.ndim:
2 3

x.shape and y.shape:
(2, 2) (2, 1, 2)