如何在循环中连接np.ndarray？

Question

I have some ndarray that values is constructed in loop. I want to concatenate these ndarray to a single array with axis 0. How could I do it in python? This is my example

input: 1x2x32x32x64,1x2x32x32x64,1x2x32x32x64,1x2x32x32x64
output 4x2x32x32x64

What I have done:

import numpy as np
A_concate=np.array([])
for i in range (4):
    a_i = np.random.rand(1,2,32,32,64)
    print (a_i.shape)
    A_concate= np.concatenate(A_concate,a_i, axis=0)
print (A_concate.shape)

The error

 Traceback (most recent call last): File "python", line 6, in <module> TypeError: Argument given by name ('axis') and position (2) 

Online code: https://repl.it/repls/HugeKnownSolidstatedrive

First solution using vstack

import numpy as np
A_concate=[]
for i in range (4):
    a_i = np.random.rand(1,2,32,32,64)
    print (a_i.shape)
    A_concate.append(a_i)
A_concate=np.vstack((A_concate))
print (A_concate.shape)

Answer 1

Here is a solution with numpy.vstack

import numpy as np
A_stack = np.random.rand(1,2,32,32,64)
for i in range (3):
    a_i = np.random.rand(1,2,32,32,64)
    A_stack= np.vstack([A_stack,a_i])
print (A_stack.shape) # Outputs (4, 2, 32, 32, 64)