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Issue

Below is a list of dates in the string format(MM/DD/YYYY).
I'm trying to sort them in ascending order(oldest to most-recent date) using .sort() but getting wrong results.

List before sort

listOfDates = ['07/25/2022', '07/19/2022', '04/19/2022', '02/18/2022', '01/18/2022', '10/20/2021', '10/27/2021', '11/26/2021', '12/23/2021', '01/05/2022', '01/07/2022', '01/18/2022', '01/21/2022', '01/24/2022', '02/24/2022', '02/25/2022', '03/16/2022', '03/25/2022', '04/29/2022', '05/10/2022', '05/11/2022', '05/31/2022', '06/08/2022', '06/10/2022', '06/13/2022', '06/14/2022', '07/14/2022']

Results using listOfDates.sort()

The problem here is that it appears to be sorting by month and not chronologically. Notice it starts at 01/05/2022 and goes up to 07/25/2022 and then continues at 10/20/2021 until ending 12/23/2021

['01/05/2022', '01/07/2022', '01/18/2022', '01/18/2022', '01/21/2022', '01/24/2022', '02/18/2022', '02/24/2022', '02/25/2022', '03/16/2022', '03/25/2022', '04/19/2022', '04/29/2022', '05/10/2022', '05/11/2022', '05/31/2022', '06/08/2022', '06/10/2022', '06/13/2022', '06/14/2022', '07/14/2022', '07/19/2022', '07/25/2022', '10/20/2021', '10/27/2021', '11/26/2021', '12/23/2021']

Expecting

That the dates are ordered in the list by descending order with the first element starting 10/20/2021 and the final element in the list is 07/25/2022

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4
  • 1
    Well, you're sorting strings, not dates. Commented Jul 27, 2022 at 14:41
  • You are sorting them according to their string values. Instead, sort them according to their date value. You can parse them to dates using datetime.strptime docs.python.org/3/library/… Commented Jul 27, 2022 at 14:42
  • Why do you expect strings to be sorted as dates? If you want to sort them as dates, specify a key argument to .sort() which converts the string to a date. docs.python.org/3/howto/sorting.html#key-functions Commented Jul 27, 2022 at 14:42
  • I recommend using the datetime module. Personally, I would iterate through your list and convert each date to a datetime object in a new list. Then, you can use sort functions in the module that intelligently will base the sort on chronology. Commented Jul 27, 2022 at 14:44

1 Answer 1

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0

You can do something like this

import datetime

sortedDates = sorted([datetime.datetime.strptime(item, '%m/%d/%Y') for item in listOfDates])

[item.strftime('%m/%d/%Y') for item in sortedDates]
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