Open In App
Related Articles

Add a key:value pair to dictionary in Python

Improve
Improve
Improve
Like Article
Like
Save Article
Save
Report issue
Report

Dictionary in Python is an unordered collection of data values, used to store data values like a map, which unlike other Data Types that hold only single value as an element, Dictionary holds key:value pair. While using Dictionary, sometimes, we need to add or modify the key/value inside the dictionary. Let’s see how to add a key:value pair to dictionary in Python. 

Code #1: Using Subscript notation This method will create a new key:value pair on a dictionary by assigning a value to that key. 

Python3

# Python program to add a key:value pair to dictionary
 
dict = {'key1':'geeks', 'key2':'for'}
print("Current Dict is: ", dict)
   
# using the subscript notation
# Dictionary_Name[New_Key_Name] = New_Key_Value
 
dict['key3'] = 'Geeks'
dict['key4'] = 'is'
dict['key5'] = 'portal'
dict['key6'] = 'Computer'
print("Updated Dict is: ", dict)

                    
Output:

Current Dict is: {‘key2’: ‘for’, ‘key1’: ‘geeks’} Updated Dict is: {‘key3’: ‘Geeks’, ‘key5’: ‘portal’, ‘key6’: ‘Computer’, ‘key4’: ‘is’, ‘key1’: ‘geeks’, ‘key2’: ‘for’}

Time Complexity: O(1)
Auxiliary Space: O(1)

Code #2: Using update() method 

Python3

dict = {'key1':'geeks', 'key2':'for'}
print("Current Dict is: ", dict)
 
# adding dict1 (key3, key4 and key5) to dict
dict1 = {'key3':'geeks', 'key4':'is', 'key5':'fabulous'}
dict.update(dict1)
 
# by assigning
dict.update(newkey1 ='portal')
print(dict)

                    
Output:

Current Dict is: {‘key2’: ‘for’, ‘key1’: ‘geeks’} {‘newkey1’: ‘portal’, ‘key4’: ‘is’, ‘key2’: ‘for’, ‘key1’: ‘geeks’, ‘key5’: ‘fabulous’, ‘key3’: ‘geeks’}

Time Complexity: O(1)
Auxiliary Space: O(1)

Code #3: Taking Key:value as input 

Python3

# Let's add key:value to a dictionary, the functional way
 
# Create your dictionary class
class my_dictionary(dict):
 
    # __init__ function
    def __init__(self):
        self = dict()
         
    # Function to add key:value
    def add(self, key, value):
        self[key] = value
 
# Main Function
dict_obj = my_dictionary()
 
# Taking input key = 1, value = Geek
dict_obj.key = input("Enter the key: ")
dict_obj.value = input("Enter the value: ")
 
dict_obj.add(dict_obj.key, dict_obj.value)
dict_obj.add(2, 'forGeeks')
 
print(dict_obj)

                    

Output:

 {'1': 'Geeks', 2: 'forGeeks'}

Time Complexity: O(1)
Auxiliary Space: O(n)

Code #4: Using a dictionary comprehension 

For example, you can create a new dictionary that adds a key:value pair to an existing dictionary like this:

Python3

existing_dict = {'key1': 'value1', 'key2': 'value2'}
new_key = 'key3'
new_value = 'value3'
 
updated_dict = {**existing_dict, new_key: new_value}
print(updated_dict)
#This code is contributed by Edula Vinay Kumar Reddy

                    

Output
{'key1': 'value1', 'key2': 'value2', 'key3': 'value3'}

This creates a new dictionary called updated_dict that contains all the key:value pairs from existing_dict, as well as the new key:value pair ‘key3’: ‘value3’.

Time Complexity: O(n)
Auxiliary Space: O(n)



Last Updated : 24 Feb, 2023
Like Article
Save Article
Previous
Next
Share your thoughts in the comments
Similar Reads