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Add a key:value pair to dictionary in Python

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  • Last Updated : 30 Dec, 2022
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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. 


# 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)


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

Code #2: Using update() method 


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'}
# by assigning
dict.update(newkey1 ='portal')


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

Code #3: Taking Key:value as input 


# 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')


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

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:


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


{'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)

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