如何将纪元时间转换为字符串？

Question

我有一个数据数组 10000*3 需要保存为 csv 文件。下面是我的伪代码，但我不知道如何仅使用 numpy（不是 pandas）来实现它。有人知道该怎么做?

import numpy as np
import time 
arr = np.random.randn(10000, 3)

# That need  arr[0,0] = time.time(), arr[i, 0] = time.time()  + i
arr[:,0] = time.time() + 1

# And after that, I need to  column 1 to datatime string(like "2021-02-12 12:12:12")
arr[:,0] need to apply `time.strftime("%Y-%m-%d %H:%M:%S", time.localtime(item))` this function.

# After that, the data type is, column1:str, column2:float, column3:float and to save it as a csv file.

Answer 1

这可以通过import csv（预装python默认包）来完成。有关示例，请参阅本教程：https://www.pythontutorial.net/python-basics/python-write-csv-file/

with open('countries.csv', 'w', encoding='UTF8') as f:
    writer = csv.writer(f)

    # write the header
    writer.writerow(header)

    # write the data
    for row in arr:
         writer.writerow(row)