将2D数组连接成字符串导致分割错误

# 二维数组连接成字符串
def join_2d_array(array):
    joined_str = ''
    for i in range(len(array)):
        for j in range(len(array[i])):
            joined_str += str(array[i][j])
            if j != len(array[i]) - 1:
                joined_str += ','
        if i != len(array) - 1:
            joined_str += ';'
    return joined_str

# 测试代码
array = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
joined_str = join_2d_array(array)
print(joined_str)  # 输出：1,2,3;4,5,6;7,8,9

# 字符串分割为二维数组
def split_to_2d_array(joined_str):
    array = []
    rows = joined_str.split(';')
    for row in rows:
        array.append(row.split(','))
    return array

# 测试代码
split_array = split_to_2d_array(joined_str)
print(split_array)  # 输出：[[1, 2, 3], [4, 5, 6], [7, 8, 9]]