Python - Insertion at the beginning in OrderedDict

Python – Insertion at the beginning in OrderedDict

Difficulty Level : Basic
Last Updated : 27 Feb, 2020

Given an ordered dict, write a programm to insert items in beginning of ordered dict.

Examples –

Input: 
original_dict = {'a':1, 'b':2}
item to be inserted ('c', 3)

Output:  {'c':3, 'a':1, 'b':2}

Input: 
original_dict = {'akshat':1, 'manjeet':2}
item to be inserted ('nikhil', 3)

Output:  {'nikhil':3, 'akshat':1, 'manjeet':2}

Below are various methods to insert items in starting of ordered dict.

Method #1: Using OrderedDict.move_to_end()

# Python code to demonstrate
# insertion of items in beginning of ordered dict
from collections import OrderedDict
  
# initialising ordered_dict
iniordered_dict = OrderedDict([('akshat', '1'), ('nikhil', '2')])
  
# inserting items in starting of dict 
iniordered_dict.update({'manjeet':'3'})
iniordered_dict.move_to_end('manjeet', last = False)
  
# print result
print ("Resultant Dictionary : "+str(iniordered_dict))

Output:

Resultant Dictionary : OrderedDict([(‘manjeet’, ‘3’), (‘akshat’, ‘1’), (‘nikhil’, ‘2’)])

Method #2: Using Naive Approach

This method only works in case of unique keys

# Python code to demonstrate
# insertion of items in beginning of ordered dict
from collections import OrderedDict
  
# initialising ordered_dict
ini_dict1 = OrderedDict([('akshat', '1'), ('nikhil', '2')])
ini_dict2 = OrderedDict([("manjeet", '4'), ("akash", '4')])
  
# adding in beginning of dict
both = OrderedDict(list(ini_dict2.items()) + list(ini_dict1.items()))
  
# print result
print ("Resultant Dictionary :"+str(both))

Output:

Resultant Dictionary :OrderedDict([(‘manjeet’, ‘4’), (‘akash’, ‘4’), (‘akshat’, ‘1’), (‘nikhil’, ‘2’)])

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