Add a key:value pair to dictionary in Python
Last Updated :
24 Feb, 2023
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
dict = { 'key1' : 'geeks' , 'key2' : 'for' }
print ("Current Dict is : ", dict )
dict [ 'key3' ] = 'Geeks'
dict [ 'key4' ] = 'is'
dict [ 'key5' ] = 'portal'
dict [ 'key6' ] = 'Computer'
print ("Updated Dict is : ", dict )
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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 )
dict1 = { 'key3' : 'geeks' , 'key4' : 'is' , 'key5' : 'fabulous' }
dict .update(dict1)
dict .update(newkey1 = 'portal' )
print ( dict )
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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
class my_dictionary( dict ):
def __init__( self ):
self = dict ()
def add( self , key, value):
self [key] = value
dict_obj = my_dictionary()
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)
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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)
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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)
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