How do I sort this list in Python, if my date is in a String?

Question

[{'date': '2010-04-01', 'people': 1047, 'hits': 4522}, {'date': '2010-04-03', 'people': 617, 'hits': 2582}, {'date': '2010-04-02', 'people': 736, 'hits': 3277}]

Suppose I have this list. How do I sort by "date", which is an item in the dictionary. But, "date" is a string...

score 45 · Accepted Answer · answered Apr 07 '10 at 01:38

45

.sort(key=lambda x: datetime.datetime.strptime(x['date'], '%Y-%m-%d'))

answered Apr 07 '10 at 01:38

Ignacio Vazquez-Abrams

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this looks cool but i got "None" for an answer when i tried it! – Matt Phillips Apr 07 '10 at 01:43
9

Most `list` methods work in-place, instead of returning the list. – Ignacio Vazquez-Abrams Apr 07 '10 at 01:44
2

I like the flexibility of this answer. In my case, I had to resort to '%m/%d/%Y'. – Wok Mar 11 '14 at 14:42
Additional context on @IgnacioVazquez-Abrams comment: when he says, "works in place", he's saying you do not need to set a variable. You can simply run the code. – B-Tron of the Autobots Jun 24 '22 at 18:09

Alex Martelli · Answer 2 · 2010-04-07T02:36:29.033

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Fortunately, ISO format dates, which seems to be what you have here, sort perfectly well as strings! So you need nothing fancy:

import operator
yourlistofdicts.sort(key=operator.itemgetter('date'))

edited Apr 07 '10 at 02:36

answered Apr 07 '10 at 01:41

Alex Martelli

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score 18 · Answer 3 · answered Apr 07 '10 at 02:37

18

Satoru.Logic's solution is clean and simple. But, per Alex's post, you don't need to manipulate the date string to get the sort order right...so lose the .split('-')

This code will suffice:

records.sort(key=lambda x:x['date'])

answered Apr 07 '10 at 02:37

damzam

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...And once again the simplest, most Pythonic, and correct answer is hastily brushed aside when the asker is too hasty *sighs*. – Humphrey Bogart Apr 07 '10 at 02:41
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Upvoted for simplicity, but definitely requires dates to be in YYYY-MM-DD format (which therefore sort similarly as strings). – dkamins Apr 07 '10 at 07:23

score 4 · Answer 4 · answered Apr 07 '10 at 01:52

In python 2.6 you can use soerted w/operator.itemgetter. Since date is YYYY-MM-DD it is sorted even though its a string cause its largest to smallest - i use that format all the time for this reason

>>> import operator
>>> l = [{'date': '2010-04-01','people': 1047, 'hits': 4522}, 
         {'date': '2010-04-03', 'people': 617, 'hits': 2582}, 
         {'date': '2010-04-02', 'people': 736, 'hits': 3277}]
>>> sorted( l, key = operator.itemgetter('date') )
[{'date': '2010-04-01', 'hits': 4522, 'people': 1047}, {'date': '2010-04-02', 'hits': 3277, 'people': 736}, {'date': '2010-04-03', 'hits': 2582, 'people': 617}]

score 2 · Answer 5 · answered Apr 07 '10 at 01:40

2

records = [
     {'date': '2010-04-01', 'people': 1047, 'hits': 4522}, 
     {'date': '2010-04-03', 'people': 617, 'hits': 2582}, 
     {'date': '2010-04-02', 'people': 736, 'hits': 3277}
     ]
records.sort(key=lambda x: x['date'].split('-'))

answered Apr 07 '10 at 01:40

satoru

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Note that this sort won't work if the dates aren't zero-filled. For, example 2-1 would come after 10-1, even though February comes before October. – Rose Perrone Jul 27 '12 at 23:06

How do I sort this list in Python, if my date is in a String?

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