Python dictionary update() method [With Examples]

This Python article will provide an in-depth understanding of the Python dictionary values() method, which allows us to add new values to a dictionary.

In addition, we also discuss its usage and some practical examples.

Dictionary update() method in Python

Below are the topics that we are doing to discuss in this article:

• Introduction to Python Dictionary update() method
• Syntax of the update() method
• Purpose and use cases of the update() method

Python Dictionary update() method

The update() method is a built-in function in Python that allows you to update the contents of a dictionary by adding new key-value pairs or modifying existing ones. It takes one or more Python dictionaries or iterable objects with key-value pairs as arguments and integrates them into the target dictionary.

The syntax for using the update() method is as follows:

dictionary.update(iterable, **kwargs)

• dictionary: The target dictionary is to be updated.
• iterable: A dictionary or an iterable object containing key-value pairs to be added or updated in the target dictionary.
• **kwargs: Optional keyword arguments representing additional key-value pairs.

Return:

The update() method does not return any value; instead, it directly modifies the target Python dictionary.

update() method in Python Dictionary Examples

Here are some examples to help you understand the update() method more effectively:

Example#1 Updating a dictionary with another dictionary

Let’s assume we have two Python dictionaries containing the populations of some US states. We want to merge these Python dictionaries and update the population of a particular state.

populations1 = {'California': 39538223, 'Texas': 29145505}
populations2 = {'Texas': 29145506, 'New York': 20201249}
populations1.update(populations2)
print(populations1)

In this example, we have two Python dictionaries with populations of some US states. We update populations1 with populations2, which modifies the population of Texas and adds the population of New York to populations1.

Output:

Example#2 Updating a dictionary with an iterable object (list of tuples)

Suppose we have a Python dictionary containing the capitals of some US states and want to update this dictionary with new data provided in a Python list of tuples.

state_capitals1 = {'California': 'Sacramento', 'Texas': 'Austin'}
new_data = [('Texas', 'Austin'), ('New York', 'Albany')]
state_capitals1.update(new_data)
print(state_capitals1)

In this example, we have a Python dictionary with the capitals of some US states, and new data is provided in a Python list of tuples. We update state_capitals1 with new_data, which adds the capital of New York to state_capitals1. The capital of Texas remains the same as it was not updated in the new data.

Output:

Example#3 Updating a dictionary using keyword arguments

Let’s say we have a Python dictionary containing abbreviations of some US states, and we want to update this Python dictionary with new abbreviations.

state_abbreviations = {'California': 'CA', 'Texas': 'TX'}
state_abbreviations.update(Texas='TX', NewYork='NY')
print(state_abbreviations)

In this example, we have a Python dictionary with abbreviations of some US states. We update state_abbreviations using keyword arguments, which adds the abbreviation for New York to state_abbreviations. The abbreviation of Texas remains the same as it was not updated in the keyword arguments.

Output:

Conclusion

The Python dictionary update() method is a powerful and convenient tool for modifying Python dictionaries. It allows you to add new key-value pairs or update existing ones from other dictionaries, iterable objects, or keyword arguments.

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