How to Update a Dictionary in Python

This article explores updating dictionaries in Python, where keys of any type map to values, focusing on various methods to modify key-value pairs in this versatile data structure.

Update a Dictionary in Python

Below, are the approaches to Update a Dictionary in Python:

• Using with Direct assignment
• Using the dict() constructor
• Using the copy() and update() methods
• Using the **kwargs syntax with a function

Update a Dictionary Using the Direct Assignment

This below apporach code updates a dictionary (dictionary1) by directly assigning a new value to an existing key (“b”) and adding a new key-value pair (“c”: 4), showcasing how to modify and extend dictionaries using direct assignment. The final updated dictionary is then printed.

Python

# original dictionary
dictionary1 = {"a": 1, "b": 2}

# update value for an exisitng key
dictionary1["b"] = 3

# add a new key-value pair
dictionary1["c"] = 4

# printing result dicitonary
print(dictionary1)

Output

{'a': 1, 'c': 4, 'b': 3}

Update a Dictionary Using dict() constructor

The below apporach code updates a dictionary using the dict() constructor by passing a sequence of key-value pairs as arguments to create a new dictionary or by using an existing dictionary and adding new key-value pairs to it.

Python

# Creating a new dictionary
main_dict = dict(a=1, b=2)

# Updating the dictionary using the dict() constructor
updated_dict = dict(main_dict, c=3, d=4)

print(updated_dict)

Output

{'a': 1, 'c': 3, 'b': 2, 'd': 4}

Update a Dictionary Using the copy() and update() methods

The below approach code updates a dictionary (main_dict) by creating a copy (updated_dict) using the copy() method, and then using the update() method to add new key-value pairs (‘c’: 3, ‘d’: 4) to the copied dictionary. The final updated dictionary is then printed.

Python

main_dict = {'a': 1, 'b': 2}

# Create a copy of the original dictionary
updated_dict = main_dict.copy()

# Update the copied dictionary with new key-value pairs
updated_dict.update({'c': 3, 'd': 4})

print(updated_dict)

Output

{'a': 1, 'c': 3, 'b': 2, 'd': 4}

Update a Dictionary Using the **kwargs with a function

The below approach code uses the **kwargs syntax within a function. This approach allows us to pass key-value pairs as keyword arguments to a function and update the dictionary using these arguments.

Python

# Define a function that takes a dictionary and **kwargs
def update_dict(input_dict, **kwargs):
    # Update the input_dict with the provided keyword arguments
    input_dict.update(kwargs)

# Create an initial dictionary
dict = {'a': 1, 'b': 2}

# Call the update_dict function with **kwargs to update the dictionary
update_dict(dict, c=3, d=4)

# Print the updated dictionary
print(dict)

Output

{'a': 1, 'c': 3, 'b': 2, 'd': 4}

Conclusion

In conclusion, the methods discussed above for update the dictionary in Python. In Python, dictionary updating methods such as dict() constructor, update(), copy() and update() methods, and the **kwargs syntax within functions enable efficient manipulation of dictionaries. These versatile techniques facilitate the creation, modification, and merging of dictionaries with ease, enhancing flexibility in managing key-value pairs.