Find the key for the latest date value represented as string

Question

How do I find the key for the latest date value of a dictionary where the dates are represented as strings?

I tried using max(date, key=date.get) as in Getting key with maximum value in dictionary?, but it returns wrong results:

date = {"sale_date": "2018-02-17 20:11:37.017298",
        "buy_date": "2018-02-2 20:11:37.017298"}

latest = max(date, key=date.get)

This returns "buy_date" but clearly the result should be "sale_date".

Mehrdad Pedramfar · Answer 1 · 2018-04-30T12:52:44.293

1

You can use something like this:

> date={"sale_date":"2018-02-17 20:11:37.017298","buy_date":"2018-02-1 20:11:37.017298"}
> sorted([(value,key) for key,value in date.items()], key=lambda x:x[1])[0][1]
'sale_date'

by adding reversed=True to the sorted function, you can have it reversed.

edited Apr 30 '18 at 12:52

answered Apr 30 '18 at 09:47

Mehrdad Pedramfar

10,941
4
38
59

whatever the condition is this code always gives me 'sale_date' – Shashank Srivastava Apr 30 '18 at 12:05
@ShashankSrivastava I updated my answer, there was a key mismatch there. it gave you the earliest always, now it returns the latest. – Mehrdad Pedramfar Apr 30 '18 at 12:53
[datetime.datetime(2018, 3, 18, 8, 6, 18, 924753), datetime.datetime(2018, 3, 18, 8, 6, 10, 795445)] – Shashank Srivastava Apr 30 '18 at 13:35
i found my datetime object like this – Shashank Srivastava Apr 30 '18 at 13:36
get `max` or `min` from that. – Mehrdad Pedramfar Apr 30 '18 at 14:15

Vikas Periyadath · Answer 2 · 2018-04-30T09:57:29.750

0

If your values are in str format you can change it to date format, date is comparable So you can take the max to get latest date, Also for finding key with value in python you can try the below method:

dt={"sale_date":"2018-02-17 20:11:37.017298",
      "buy_date":"2018-02-1 20:11:37.017298" }
l = [datetime.datetime.strptime(j, "%Y-%m-%d %H:%M:%S.%f") for j in dt.values()]
for k,v in dt.items():
    if v == str(max(l)):
        print(k)

Avoid giving variables name like date, string... etc

edited Apr 30 '18 at 09:57

answered Apr 30 '18 at 09:51

Vikas Periyadath

3,088
1
21
33

successfully runs on local but when i upload it to server this gives me strptime() argument 1 must be string, not datetime.datetime – Shashank Srivastava Apr 30 '18 at 11:43
strptime() argument 1 must be string, not datetime.datetime – Shashank Srivastava Apr 30 '18 at 11:43
So just try only with `l = [ j for j in dt.values()]` this instead of strptime – Vikas Periyadath Apr 30 '18 at 11:45
@ShashankSrivastava what is error with posted code in your question , its working fine when I'am trying – Vikas Periyadath Apr 30 '18 at 11:52
@ Vikas Damodar what ever the condition is this always gives me "sale_date" – Shashank Srivastava Apr 30 '18 at 12:03
[datetime.datetime(2018, 3, 18, 8, 6, 18, 924753), datetime.datetime(2018, 3, 18, 8, 6, 10, 795445)] i found my datetime object like this – Shashank Srivastava Apr 30 '18 at 13:34
You don't need to keep the datetimes in an intermediate list. You could just use a custom key function like: `max(my_dict, key=lambda x: datetime.datetime.strptime(date[x], "%Y-%m-%d %H:%M:%S.%f"))` – Georgy Feb 13 '20 at 13:13

Find the key for the latest date value represented as string

2 Answers2