How to Concatenate Dictionaries in Python?

To concatenate dictionaries in Python, you can use the update() method or the {**dict1, **dict2} syntax. Here’s how you can use each method:

1. Using the update() method: The update() method allows you to merge the key-value pairs from one dictionary into another. 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 this example, we use the update() method on dict1 to merge the key-value pairs from dict2 into it. The update() method modifies the original dictionary (dict1) in place.

2. Using the {**dict1, **dict2} syntax (Python 3.5 and above): This syntax allows you to create a new dictionary by unpacking the key-value pairs from multiple dictionaries. Here’s an example:

dict1 = {'a': 1, 'b': 2}
dict2 = {'c': 3, 'd': 4}

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

In this example, we create a new dictionary concatenated_dict by unpacking the key-value pairs from dict1 and dict2 using the {**dict1, **dict2} syntax.

Note that if there are duplicate keys in the dictionaries being concatenated, the value from the rightmost dictionary takes precedence. For example:

dict1 = {'a': 1, 'b': 2}
dict2 = {'b': 3, 'c': 4}

dict1.update(dict2)
print(dict1)  # Output: {'a': 1, 'b': 3, 'c': 4}

In this case, the value of 'b' in dict1 is overwritten by the value from dict2.

Choose the method that suits your needs. If you want to modify one of the original dictionaries, use the update() method. If you want to create a new dictionary with the concatenated key-value pairs, use the {**dict1, **dict2} syntax.