Find the nearest 5 dates from a list in Python

Question

I have a list of datetime objects and want to find the closest 5 (or 6 or 7 etc.) dates that correspond with my specified date.

For instance:

datelist
>>>> [datetime.date(2017, 3, 4), datetime.date(2017, 3, 6), datetime.date(2017, 3, 12), datetime.date(2017, 3, 27), datetime.date(2017, 3, 27), datetime.date(2017, 3, 29), datetime.date(2017, 3, 29), datetime.date(2017, 4, 2), datetime.date(2017, 4, 4)]

If I type:

my_date = datetime.date(2017, 4, 2)
nearest_list = find_nearest(datelist, my_date)  # Functionality I want!

print nearest_list
>>>> [datetime.date(2017, 3, 27), datetime.date(2017, 3, 29), datetime.date(2017, 3, 29), datetime.date(2017, 4, 2), datetime.date(2017, 4, 4)]

I should receive a list of the nearest 5 dates.

I know that I could find the nearest date and take the two list elements either side of this (as datelist is sorted) but this is difficult when the nearest date may be the first or last element (i.e. no items before or after, respectively).

jpp · Accepted Answer · 2018-05-18 11:15:10Z

6

You can use sorted with a custom function:

res = sorted(datelist, key=lambda x: abs(x-my_date))[:5]

[datetime.date(2017, 4, 2),
 datetime.date(2017, 4, 4),
 datetime.date(2017, 3, 29),
 datetime.date(2017, 3, 29),
 datetime.date(2017, 3, 27)]

answered May 18, 2018 at 11:15

jpp

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1 Comment

George K Over a year ago

Well that's pretty neat

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