Python | Sort given list of dictionaries by date

Given a list of dictionary, the task is to sort the dictionary by date. Let’s see a few methods to solve the task.

Method #1: Using naive approach

# Python code to demonstrate
# sort a list of dictionary
# where value date is in string

# Initialising list of dictionary
ini_list = [{'name':'akash', 'd.o.b':'1997-03-02'},
            {'name':'manjeet', 'd.o.b':'1997-01-04'},
            {'name':'nikhil', 'd.o.b':'1997-09-13'}]

# printing initial list
print ("initial list : ", str(ini_list))

# code to sort list on date
ini_list.sort(key = lambda x:x['d.o.b'])

# printing final list
print ("result", str(ini_list))

Output:

initial list : [{‘name’: ‘akash’, ‘d.o.b’: ‘1997-03-02’}, {‘name’: ‘manjeet’, ‘d.o.b’: ‘1997-01-04’}, {‘name’: ‘nikhil’, ‘d.o.b’: ‘1997-09-13’}]

result [{‘name’: ‘manjeet’, ‘d.o.b’: ‘1997-01-04’}, {‘name’: ‘akash’, ‘d.o.b’: ‘1997-03-02’}, {‘name’: ‘nikhil’, ‘d.o.b’: ‘1997-09-13’}]

Method #2: Using datetime.strptime and lambda

# Python code to demonstrate
# sort a list of dictionary
# where value date is in a string

from datetime import datetime

# Initialising list of dictionary
ini_list = [{'name':'akshat', 'd.o.b':'1997-09-01'},
            {'name':'vashu', 'd.o.b':'1997-08-19'},
            {'name':'manjeet', 'd.o.b':'1997-01-04'},
            {'name':'nikhil', 'd.o.b':'1997-09-13'}]

# printing initial list
print ("initial list : ", str(ini_list))

# code to sort list on date
ini_list.sort(key = lambda x: datetime.strptime(x['d.o.b'], '%Y-%m-%d'))

# printing final list
print ("result", str(ini_list))

Output:

initial list : [{‘d.o.b’: ‘1997-09-01’, ‘name’: ‘akshat’}, {‘d.o.b’: ‘1997-08-19’, ‘name’: ‘vashu’}, {‘d.o.b’: ‘1997-01-04’, ‘name’: ‘manjeet’}, {‘d.o.b’: ‘1997-09-13’, ‘name’: ‘nikhil’}]

result [{‘d.o.b’: ‘1997-01-04’, ‘name’: ‘manjeet’}, {‘d.o.b’: ‘1997-08-19’, ‘name’: ‘vashu’}, {‘d.o.b’: ‘1997-09-01’, ‘name’: ‘akshat’}, {‘d.o.b’: ‘1997-09-13’, ‘name’: ‘nikhil’}]

Method #3: Using operator.itemgetter

# Python code to demonstrate
# sort a list of dictionary
# where value date is in string

import operator

# Initialising list of dictionary
ini_list = [{'name':'akash', 'd.o.b':'1997-03-02'},
            {'name':'manjeet', 'd.o.b':'1997-01-04'},
            {'name':'nikhil', 'd.o.b':'1997-09-13'}]

# printing initial list
print ("initial list : ", str(ini_list))

# code to sort list on date
ini_list.sort(key = operator.itemgetter('d.o.b'))

# printing final list
print ("result", str(ini_list))

Output:

initial list : [{‘d.o.b’: ‘1997-03-02’, ‘name’: ‘akash’}, {‘d.o.b’: ‘1997-01-04’, ‘name’: ‘manjeet’}, {‘d.o.b’: ‘1997-09-13’, ‘name’: ‘nikhil’}]

result [{‘d.o.b’: ‘1997-01-04’, ‘name’: ‘manjeet’}, {‘d.o.b’: ‘1997-03-02’, ‘name’: ‘akash’}, {‘d.o.b’: ‘1997-09-13’, ‘name’: ‘nikhil’}]