Add Same Key in Python Dictionary

In Python, dictionaries are a versatile data structure that allows you to store key-value pairs. If we want to add the same key with a new value to a dictionary, there are multiple methods to achieve this. In this discussion, we will explore different methods for adding the same key with a new value to a dictionary.

Add Same Key in the Dictionary in Python

Below are some of the ways by which we can add the same key in the dictionary in Python:

• Using Square Bracket Assignment
• Using the update() Method
• Using the dict() Constructor
• Using the collections.defaultdict Class

Add Same Key in Dictionary Using Square Bracket Assignment

In this method, we directly use square bracket assignment to update the value associated with the existing key in the dictionary.

Python3

# initializing dictionary
my_dict = {'a': 1, 'b': 2}

# Adding a new value to an existing key using square bracket assignment
my_dict['a'] = 3

# Displaying the result
print("Square Bracket Assignment:", my_dict)

Output

Square Bracket Assignment: {'a': 3, 'b': 2}

Add Same Key in Dictionary Using update() Method

In this approach, update() method is used to modify the dictionary. Here we can add a new key-value pair or update an existing key with a new value.

Python3

# initializing dictionary
my_dict = {'a': 1, 'b': 2}

# Using the update() method to add a new key-value pair or update an existing one
my_dict.update({'a': 3})

# Printing dictionary
print("update() Method:", my_dict)

Output

update() Method: {'a': 3, 'b': 2}

Add Same Key in Dictionary Using the dict() Constructor

In this approach, we use the dict() constructor to create a new dictionary by merging the existing dictionary with a new key-value pair or updating an existing key with a new value.

Python3

# initializing dictionary
my_dict = {'a': 1, 'b': 2}

# Using the dict() constructor to add a new key-value pair or update an existing one
my_dict = dict(my_dict, a=3)

# Printing dictionary
print("dict() Constructor:", my_dict)

Output

dict() Constructor: {'a': 3, 'b': 2}

Add Same Key in Dictionary Using the collections.defaultdict Class

In this method, we use the defaultdict class from the collections module. It allows setting a default value for any new keys, and we can update the value for an existing key.

Python3

from collections import defaultdict

my_dict = defaultdict(int, {'a': 1, 'b': 2})

# Adding a new value to an existing key using defaultdict
my_dict['a'] = 3

print("defaultdict Class:", dict(my_dict))

Output

defaultdict Class: {'a': 3, 'b': 2}

Conclusion

We have covered easy methods on “How to Add Same Key in Dictionary Python”, we can easily add the same key value in dictionary using these methods. Adding values in a dictionary is very important for data manipulation, updation, deletion, etc.