How do I merge dicts in Python safely and idiomatically?

In Python, merging dictionaries can be done in several ways, but to do it safely and idiomatically, you should consider the effects of overwriting keys and ensure compatibility among your data structures. Below are some common methods to merge dictionaries in Python:

Merging Dictionaries Using the Update Method

The update() method allows you to merge one dictionary into another. It will overwrite the keys from the first dictionary if they exist in the second.

# Example of merging with update dict1 = {'a': 1, 'b': 2} dict2 = {'b': 3, 'c': 4} dict1.update(dict2) print(dict1) # Output: {'a': 1, 'b': 3, 'c': 4}

Using the Pipe Operator (Python 3.9+)

Starting in Python 3.9, you can use the | operator to merge dictionaries. This method does not modify the original dictionaries, but instead returns a new one.

# Example of merging using the pipe operator dict1 = {'a': 1, 'b': 2} dict2 = {'b': 3, 'c': 4} merged_dict = dict1 | dict2 print(merged_dict) # Output: {'a': 1, 'b': 3, 'c': 4}

Dictionary Comprehension

You can also use dictionary comprehension for a more manual but flexible approach.

# Example of merging using dictionary comprehension dict1 = {'a': 1, 'b': 2} dict2 = {'b': 3, 'c': 4} merged_dict = {k: v for d in [dict1, dict2] for k, v in d.items()} print(merged_dict) # Output: {'a': 1, 'b': 3, 'c': 4}

python merge dictionaries update method dictionary comprehension Python 3.9 pipe operator

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