How to sort array with unique elements by datetime (Python)

Question

So my issue is that I exported an excel file as a csv file. I've imported the file into Python and added it to a matrix which looks like:

A = [[1, '13/04/2015 12:22:45'],
     [2, '13/04/2015 12:22:46'],
     [3, '12/04/2015 12:30:00']]

I want to sort this by date and time. I have found several solutions that sort datetimes using the built in sorted() function, but none of the examples have additional array columns with other values.

Thanks for your help!

Could you share some code for your sorting for us to see what you have tried? — Daniel Casserly
– Daniel Casserly, Commented Apr 13, 2015 at 21:52

mgilson · Accepted Answer · 2015-04-13 21:45:07Z

3

First, you probably want to be able to construct datetime objects from the strings that you have for comparison purposes:

import datetime
def make_datetime(lst):
    date_str = lst[1]
    return datetime.datetime.strptime(date_str, '%d/%m/%Y %H:%M:%s')

Now you can use this as the key to your sort function:

sorted_A = sorted(A, key=make_datetime)

answered Apr 13, 2015 at 21:45

mgilson

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1 Comment

zwelz Over a year ago

Thanks for your help! I didn't realise that I had to convert to a datetime object first. My original code was sorting based on the string like zachgates7's answer below. Thanks again!

Zach Gates · Accepted Answer · 2015-04-13 21:49:29Z

0

You can sort by the second element (your datetime) using

A.sort(key=lambda i: i[1])

This is assuming that you want to sort by the string, rather than the actual date. Otherwise, take a look at mgilson's answer.

edited Apr 13, 2015 at 21:49

answered Apr 13, 2015 at 21:44

Zach Gates

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2 Comments

mgilson Over a year ago

Hmmm... I think this doesn't quite work: [[1, '13/04/2015 00:00:00'], [2, '12/05/2015 00:00:00']] -- You can't compare as strings with the current date format OP is using.

khajvah Over a year ago

I took back my upvote as, for example, "12/04/2000" > "11/05/2000" is True

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