CODEWITHSUNDEEP
python
Dawn17
Dawn17

Reputation: 8297

How can I sort dates that are in String? (python)

I've only tried 

from datetime import datetime
my_dates = ['5-Nov-18', '25-Mar-17', '1-Nov-18', '7 Mar 17']
my_dates.sort(key=lambda date: datetime.strptime(date, "%d-%b-%y"))
print(my_dates)

But how can I make this work for date formats like

my_dates = ['05 Nov 2018', '25 Mar 2017', '01 Nov 2018', '07 Mar 2017']

Upvotes: 1

Views: 1986

Answers (3)

deadvoid
deadvoid

Reputation: 1300

dates can be sorted once it's a datetime object

my_dates = ['05 Nov 2018', '25 Mar 2017', '01 Nov 2018', '07 Mar 2017']
my_dates = [ dt.strptime(date, '%d %b %Y') for date in my_dates ]
print(my_dates)
# [datetime.datetime(2018, 11, 5, 0, 0), datetime.datetime(2017, 3, 25, 0, 0), datetime.datetime(2018, 11, 1, 0, 0), datetime.datetime(2017, 3, 7, 0, 0)]

my_dates.sort()
print(my_dates)
# [datetime.datetime(2017, 3, 7, 0, 0), datetime.datetime(2017, 3, 25, 0, 0), datetime.datetime(2018, 11, 1, 0, 0), datetime.datetime(2018, 11, 5, 0, 0)]

my_dates = [ date.strftime('%d %b %Y') for date in my_dates ]
print(my_dates)
# ['07 Mar 2017', '25 Mar 2017', '01 Nov 2018', '05 Nov 2018']

Upvotes: 0

r.ook
r.ook

Reputation: 13858

If all you're looking is the specific set of dates you have provided, just change up the format in strptime():

my_dates = ['05 Nov 2018', '25 Mar 2017', '01 Nov 2018', '07 Mar 2017']
my_dates.sort(key=lambda date: datetime.strptime(date, "%d %b %Y"))

# Change the last %y to %Y

However, if you have varying date formats in your list, you could prepare a list of possibly anticipated string formats and define your own function to parse against each format:

def func(date, formats):
    for frmt in formats:
        try:
            str_date = datetime.strptime(date, frmt)
            return str_date
        except ValueError:
            continue

    # might want to consider handling a scenario when nothing is returned

my_formats = ['%d-%b-%y', '%d %b %y', '%d %b %Y']
my_dates = ['5-Nov-18', '25-Mar-17', '1-Nov-18', '7 Mar 17', '05 Nov 2018', '25 Mar 2017', '01 Nov 2018', '07 Mar 2017']
my_dates.sort(key=lambda date: func(date, my_formats))
print(my_dates)

# ['7 Mar 17', '07 Mar 2017', '25-Mar-17', '25 Mar 2017', '1-Nov-18', '01 Nov 2018', '5-Nov-18', '05 Nov 2018']

The caveat here is if an unanticipated date format shows up, the function will return None so it won't be sorted properly. If that's a concern, you might want to add some handling at the end of the func() when all parsing attempts failed. Some devs might also say to avoid try...except..., but I can only come up with this way.

Upvotes: 0

A. Pond
A. Pond

Reputation: 370

One inelegant solution which comes to mind is replacing all spaces with dashes as shown below:

from datetime import datetime
my_dates = ['5-Nov-18', '25-Mar-17', '1-Nov-18', '7 Mar 17']
my_dates.sort(key=lambda date: datetime.strptime(date.replace(' ', '-'), "%d-%b-%y"))
print(my_dates)

Upvotes: 2

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