In this tutorial, we will discuss how to add a key-value pair from one dictionary to another in Python. We will go through the various methods to achieve this such as using the update() and ** unpacking techniques. By the end of this tutorial, you should have a clear understanding of how to efficiently combine dictionaries in Python.
Step 1: Create Two Dictionaries
First, let’s create two dictionaries that we will use throughout this tutorial. For simplicity, we will use dict1 and dict2.
Here’s how you would create two dictionaries in Python:
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dict1 = {'a': 1, 'b': 2} dict2 = {'c': 3, 'd': 4} |
Step 2: Using the update() Method
The first approach is to use the update() method, which is a built-in method for dictionaries. Here’s how you would use the update() method:
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dict1.update(dict2) |
Here’s the output for this code snippet:
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{'a': 1, 'b': 2, 'c': 3, 'd': 4} |
Keep in mind that using this method will update the contents of dict1 with the key-value pairs from dict2. If you want to keep dict1 unchanged, consider using one of the other methods described below.
Step 3: Using Dict Comprehension
Another approach is to use dictionary comprehension to create a new dictionary by combining the key-value pairs from the two original dictionaries. Here’s how to do this:
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combined_dict = {k: v for d in (dict1, dict2) for k, v in d.items()} |
This method creates a new dictionary called combined_dict that contains the key-value pairs from both dict1 and dict2.
Step 4: Using ** Unpacking
In Python 3.5 and later, you can use the ** unpacking operator to merge two dictionaries into a new one. This approach is concise and does not modify the original dictionaries:
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combined_dict = {**dict1, **dict2} |
By using **dict1 and **dict2, you can unpack the key-value pairs from both dictionaries and merge them into a single dictionary.
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dict1 = {'a': 1, 'b': 2} dict2 = {'c': 3, 'd': 4} # Method 1: Using the update() method dict1.update(dict2) # Method 2: Using dict comprehension combined_dict = {k: v for d in (dict1, dict2) for k, v in d.items()} # Method 3: Using ** unpacking combined_dict = {**dict1, **dict2} print(combined_dict) |
Conclusion
In this tutorial, we learned how to add key-value pairs from one dictionary to another in Python using various methods such as the update() method, dictionary comprehension, and ** unpacking. These methods make it easy for you to combine dictionaries in a manner that best suits your requirements.