如何更改现有数组的形状，同时保持内容居中并用0填充新的空格？

import numpy as np

arr = np.array([[1, 2, 3], [4, 5, 6]])

new_shape = (3, 4)  # 新的形状
new_arr = np.zeros(new_shape)  # 创建一个新的全0数组
old_shape = arr.shape  # 原始数组的形状
start_row = (new_shape[0] - old_shape[0]) // 2  # 计算起始行索引
start_col = (new_shape[1] - old_shape[1]) // 2  # 计算起始列索引
new_arr[start_row:start_row+old_shape[0], start_col:start_col+old_shape[1]] = arr  # 将原始数组复制到新数组的中间位置

padded_arr = np.pad(new_arr, ((0, new_shape[0]-old_shape[0]), (0, new_shape[1]-old_shape[1])), mode='constant', constant_values=0)