can you append to a 2d array in numpy code example

Example 1: python append to 2d array

temp_list = [[], [], [], []]
temp_list[0].append("a1")
temp_list[1].append("a2")
temp_list[2].append("a3")
temp_list[3].append("a4")

Example 2: python 2d array append

arr = []
arr.append([])
arr[0].append('aa1')
arr[0].append('aa2')