transform a list of datetimes in a pandas column to list of strings

Question

I have the following pandas dataframe

import pandas as pd
import datetime

foo = pd.DataFrame({'id': [1,2], 'time' :['[datetime.datetime(2021, 10, 20, 14, 29, 51), datetime.datetime(2021, 10, 20, 14, 46, 8)]', '[datetime.datetime(2021, 10, 20, 15, 0, 44), datetime.datetime(2021, 10, 20, 16, 13, 42)]']})
foo

   id   time
0   1   [datetime.datetime(2021, 10, 20, 14, 29, 51), datetime.datetime(2021, 10, 20, 14, 46, 8)]
1   2   [datetime.datetime(2021, 10, 20, 15, 0, 44), datetime.datetime(2021, 10, 20, 16, 13, 42)]

I would like to transform each element of the lists in the time column to a string with the format '%Y/%m/%d %H:%M:%S'

I know I can do this:

t = datetime.datetime(2021, 10, 20, 14, 29, 51)
t.strftime('%Y/%m/%d %H:%M:%S')

to yield the value '2021/10/20 14:29:51',

but I do not know how to do this operation for every string element of each list in the time column.

Any help ?

Does this answer your question? [How can I convert string to source code in python?](https://stackoverflow.com/questions/43878504/how-can-i-convert-string-to-source-code-in-python) — mosc9575, Sep 22 '22 at 18:02

Nuri Taş · Accepted Answer · 2022-09-22T18:08:14.567

1

You just need to use list comprehension inside apply after converting string lists to actual lists with eval:

foo.time.apply(lambda str_list: [item.strftime('%Y/%m/%d %H:%M:%S') for item in eval(str_list)])

edited Sep 22 '22 at 18:08

answered Sep 22 '22 at 17:40

Nuri Taş

3,828
2
4
22

Sorry, my input dataframe was wrong, I corrected it. For the corrected one this solution does not work :( – quant Sep 22 '22 at 17:57
1

I've updated the answer for the new dataframe – Nuri Taş Sep 22 '22 at 18:08
1

I was putting the `eval` to the wrong place. I need a walk ;) tnx – quant Sep 22 '22 at 18:09

score 0 · Answer 2 · answered Sep 22 '22 at 17:52

0

You can separate the list into rows first with explode and then use the dt accessor in pandas:

(foo
 .explode('time')
 .assign(time=lambda x: x.time.dt.strftime('%Y/%m/%d %H:%M:%S'))
)

answered Sep 22 '22 at 17:52

William Rosenbaum

255
2
7

transform a list of datetimes in a pandas column to list of strings

2 Answers2