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’}]

My Personal Notes

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