How to sort a list by datetime in python? [duplicate]

Question

I am writing a .py file to sort lists by time which contain the following information

date, time, emp_id, action_performed

There is a question asked about this on stackoverflow but I couldn't exactly follow(I am new to python)

I also checked out the sort function and the datetime library but couldnt get it to work.

list = 
[
('2017/09/10 13:19:38', 'employee_id', 'enrolled'),
('2017/09/10 12:15:21', 'employee_id', 'deleted'),
('2017/09/10 21:19:34', 'employee_id', 'enrolled'),
('2017/09/10 22:42:50', 'employee_id', 'deleted'),
('2017/09/10 16:53:03', 'employee_id', 'enrolled')
]

I just want to know which action was performed first. Can someone help me out?

In your case, with this date format (implying yyyy/mm/dd) as simple list.sort() would do the task. — Klaus D.
– Klaus D., Commented Sep 10, 2019 at 15:03
I also checked out the sort function and the datetime library but couldnt get it to work Show us what you tried. If you just tell us you tried something, without showing the actual code, we can't point out what you did wrong. — John Gordon
– John Gordon, Commented Sep 10, 2019 at 15:04
For your sake don't override the builtin list. When you do that you can't use the list function anymore. — Jab
– Jab, Commented Sep 10, 2019 at 15:06
Thank you for your answer. When I run 'print list.sort()', it returns me 'None', am I doing it right? — Ebenezer Isaac
– Ebenezer Isaac, Commented Sep 10, 2019 at 15:07

gmoshkin · Accepted Answer · 2019-09-10 15:12:47Z

13

from datetime import datetime
list = 
[
('2017/09/10 13:19:38', 'employee_id', 'enrolled'),
('2017/09/10 12:15:21', 'employee_id', 'deleted'),
('2017/09/10 21:19:34', 'employee_id', 'enrolled'),
('2017/09/10 22:42:50', 'employee_id', 'deleted'),
('2017/09/10 16:53:03', 'employee_id', 'enrolled')
]
sorted_list = sorted(list, key=lambda t: datetime.strptime(t[0], '%Y/%m/%d %H:%M:%S'))

Use the key parameter of the sorted function, in this case it tells the function to parse the first element of each tuple as a datetime string with the format '%Y/%m/%d %H:%M:%S' and use that value for sorting.

answered Sep 10, 2019 at 15:12

gmoshkin

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lenik · Accepted Answer · 2019-09-10 15:03:59Z

4

Try this:

sorted_list = sorted( list )

=)

answered Sep 10, 2019 at 15:03

lenik

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Comments

TheBlackHole · Accepted Answer · 2019-09-10 15:31:11Z

2

In this case, a simple list.sort() which sorts the list in place, or sorted(list) which returns a sorted copy of the list would work perfectly — as long as the dates and times follow Y/M/D H/M/S.

To get the first performed action in one line, you could use:

first_action = sorted(list)[0]

answered Sep 10, 2019 at 15:31

TheBlackHole

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