【Numpy 学习记录】np.stack 和 np.concatenate

np.stack 和 np.concatenate两个函数都是用来连接数组的， 但是他们之间还是有一些探讨之处，直接上代码，一看便知：

import numpy as np

a = np.zeros(12).reshape(4,3,)
b = np.arange(12).reshape(4,3)

# for np.stack:all input arrays must have the same shape
print(np.hstack((a, b)).shape)  # (4, 6)
print(np.vstack((a, b)).shape)  # (8, 3)
print(np.dstack((a, b)).shape)  # (4, 3, 2)

print(np.stack((a, b), axis=0).shape)  # (2, 4, 3)
print(np.stack((a, b), axis=1).shape)  # (4, 2, 3)
print(np.stack((a, b), axis=2).shape)  # (4, 3, 2)

a = np.zeros(12).reshape(2,3, 2)
b = np.arange(6).reshape(2,3, 1)
print(np.concatenate((a, b), axis=2).shape)  # (2, 3, 3)
# print(np.stack((a, b), axis=2).shape)  # error
print(np.dstack((a, b)).shape)  # (2, 3, 3)