import csv,numpy

def save_to_csv(my_list):
    print("保存数据")
# 
#    line_num = len(read_from_csv())
#    my_list_len = len(my_list)
#
#    # 访止空列表覆盖（清空）已有数据
#    if my_list_len <= 1 or my_list_len < line_num:
#        print("my_list 长度为{}",my_list_len," ,不保存！")
#        return

    str = numpy.array(my_list)
    with open('detail.csv', 'w', newline='', encoding='utf-8') as file:
        mywriter = csv.writer(file, delimiter=',')
        mywriter.writerows(str)
    print("保存数据 OK!")


def read_from_csv():
	data= []
    with  open('detail.csv', 'r', newline='', encoding='utf-8') as file :
	    reader= csv.reader(file, delimiter=',')	    
	    for row in reader:
	        data.append(row)
    return data


myarray = [
    [1, 4, 2]
    , [7, 9, 4]
    , [0, 6, 2]
]
# 保存数据
save_to_csv(myarray)

# 读取数据
data = read_from_csv()
for row in data :
    print(row )

运行结果：

保存数据
保存数据 OK!
['1', '4', '2']
['7', '9', '4']
['0', '6', '2']