Merging Two Dictionaries in a Single Expression in Python

Method 1: Using the "update()" Method

The `update()` method allows you to merge one dictionary into another. It takes another dictionary as an argument and adds its key-value pairs to the original dictionary. Here's an example:

dict1 = {'a': 1, 'b': 2}
dict2 = {'c': 3, 'd': 4}
dict1.update(dict2)
print(dict1)

Output:

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

In the above example, `dict1` is merged with `dict2` using the `update()` method. The result is stored in `dict1`, which now contains all the key-value pairs from both dictionaries.

Method 2: Using the Double Asterisk (**) Operator

Python provides a concise way to merge dictionaries using the double asterisk (**) operator. This operator, also known as the "unpacking" operator, allows you to expand a dictionary into keyword arguments. Here's an example:

dict1 = {'a': 1, 'b': 2}
dict2 = {'c': 3, 'd': 4}
merged_dict = {**dict1, **dict2}
print(merged_dict)

Output:

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

In the above example, the double asterisk operator is used to merge `dict1` and `dict2` into `merged_dict`. This creates a new dictionary containing all the key-value pairs from both dictionaries.

Method 3: Using the "dict()" Constructor

The `dict()` constructor can also be used to merge dictionaries. It takes an iterable of key-value pairs and creates a new dictionary. Here's an example:

dict1 = {'a': 1, 'b': 2}
dict2 = {'c': 3, 'd': 4}
merged_dict = dict(dict1, **dict2)
print(merged_dict)

Output:

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

In the above example, `dict1` and `dict2` are merged using the `dict()` constructor. The double asterisk operator is used to pass `dict2` as keyword arguments to the constructor, resulting in a new dictionary `merged_dict` with all the key-value pairs.

Merging two dictionaries in Python can be achieved with a single expression, providing a convenient way to combine key-value pairs from different sources. In this article, we explored three methods: using the `update()` method, the double asterisk (**) operator, and the `dict()` constructor. These methods allow you to merge dictionaries efficiently and produce a new dictionary containing all the key-value pairs. Depending on your preference and the specific use case, you can choose the method that best suits your needs.

Published on May 25, 2023

Tags: dictionary | Python