How can I sort my dates in a numpy array in order?

Question

I have this numpy array called all_periods:

array(['01/01/2021', '01/01/2022', '02/01/2021', '02/01/2022',
       '03/01/2020', '03/01/2021', '03/01/2022', '04/01/2020',
       '04/01/2021', '04/01/2022', '05/01/2020', '05/01/2021',
       '06/01/2020', '06/01/2021', '07/01/2020', '07/01/2021',
       '08/01/2020', '08/01/2021', '09/01/2020', '09/01/2021',
       '10/01/2020', '10/01/2021', '11/01/2020', '11/01/2021',
       '12/01/2020', '12/01/2021'], dtype=object)

I want to sort this by day, month and year.

When I tried using the .sort_values function it only sorted it by the day. How do I sort it by day, month, year?

Asked By: Bismah Ghafoor

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Source

Answer 1

This code is help you to sort by day,month and year:

import numpy as np
from datetime import datetime

all_periods = np.array(['01/01/2021', '01/01/2022', '02/01/2021', '02/01/2022', '03/01/2020', '03/01/2021', '03/01/2022', '04/01/2020', '04/01/2021', '04/01/2022', '05/01/2020', '05/01/2021', '06/01/2020', '06/01/2021', '07/01/2020', '07/01/2021', '08/01/2020', '08/01/2021', '09/01/2020', '09/01/2021', '10/01/2020', '10/01/2021', '11/01/2020', '11/01/2021', '12/01/2020', '12/01/2021'])

dates = [datetime.strptime(d, '%d/%m/%Y') for d in all_periods]

sorted_dates = np.sort(dates)

sorted_periods = np.array([d.strftime('%d/%m/%Y') for d in sorted_dates])

print(sorted_periods)

Result:

['03/01/2020' '04/01/2020' '05/01/2020' '06/01/2020' '07/01/2020'
 '08/01/2020' '09/01/2020' '10/01/2020' '11/01/2020' '12/01/2020'
 '01/01/2021' '02/01/2021' '03/01/2021' '04/01/2021' '05/01/2021'
 '06/01/2021' '07/01/2021' '08/01/2021' '09/01/2021' '10/01/2021'
 '11/01/2021' '12/01/2021' '01/01/2022' '02/01/2022' '03/01/2022'
 '04/01/2022']

Answered By: NIKUNJ PATEL

Answer 2

I hope, it works for you

import numpy as np
from datetime import datetime
a = np.array([
    '01/01/2021', '01/01/2022', '02/01/2021', '02/01/2022', '03/01/2020',
    '03/01/2021', '03/01/2022', '04/01/2020', '04/01/2021', '04/01/2022',
    '05/01/2020', '05/01/2021', '06/01/2020', '06/01/2021', '07/01/2020',
    '07/01/2021', '08/01/2020', '08/01/2021', '09/01/2020', '09/01/2021',
    '10/01/2020', '10/01/2021', '11/01/2020', '11/01/2021', '12/01/2020',
    '12/01/2021'
])
# sort by year, month and day
sorted(a, key=lambda x: datetime.strptime(x, '%d/%m/%Y'))

Output:

['03/01/2020', '04/01/2020', '05/01/2020', '06/01/2020', '07/01/2020', '08/01/2020', '09/01/2020', '10/01/2020', '11/01/2020', '12/01/2020', '01/01/2021', '02/01/2021', '03/01/2021', '04/01/2021', '05/01/2021', '06/01/2021', '07/01/2021', '08/01/2021', '09/01/2021', '10/01/2021', '11/01/2021', '12/01/2021', '01/01/2022', '02/01/2022', '03/01/2022', '04/01/2022']

Answered By: Muhammad Ali

Answer 3

You can simply define a sorting key function and sort the strings without any other library:

def func(x):
    x = x.split('/')
    return '.'.join(reversed(x))
    
all_periods = sorted(all_periods, key = func)

which gives

['03/01/2020', '04/01/2020', '05/01/2020', '06/01/2020', '07/01/2020', '08/01/2020', '09/01/2020', '10/01/2020', '11/01/2020', '12/01/2020', '01/01/2021', '02/01/2021', '03/01/2021', '04/01/2021', '05/01/2021', '06/01/2021', '07/01/2021', '08/01/2021', '09/01/2021', '10/01/2021', '11/01/2021', '12/01/2021', '01/01/2022', '02/01/2022', '03/01/2022', '04/01/2022']

Answered By: user19077881

Answer 4

I’d be inclined to convert them to numpy datetime64 objects and sort them directly, something like:

import numpy as np
from datetime import datetime
dates = np.array([
    '01/01/2021', '01/01/2022', '02/01/2021', '02/01/2022', '03/01/2020',  
    '03/01/2021', '03/01/2022', '04/01/2020', '04/01/2021', '04/01/2022', 
    '05/01/2020', '05/01/2021', '06/01/2020', '06/01/2021', '07/01/2020', 
    '07/01/2021', '08/01/2020', '08/01/2021', '09/01/2020', '09/01/2021', 
    '10/01/2020', '10/01/2021', '11/01/2020', '11/01/2021', '12/01/2020', 
    '12/01/2021'
])
conv_dates = np.array([
    np.datetime64(
        datetime.strptime(d, "%d/%m/%Y").strftime("%Y-%m-%d")
    ) for d in dates])
sorted_dates = np.sort(conv_dates)

Answered By: Andj

How can I sort my dates in a numpy array in order?

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