How to Efficiently Merge Two Dictionaries in Python?

How Can I Efficiently Merge Two Dictionaries in a Single Expression in Python?

Python 3.9.0 or Later:

z = x | y

Python 3.5 or Later:

z = {**x, **y}

Python 2 and Earlier:

Create a custom merge_two_dicts function:

def merge_two_dicts(x, y):
    z = x.copy()  # Start with keys and values of x
    z.update(y)    # Modifies z with keys and values of y
    return z

Usage:

z = merge_two_dicts(x, y)

Explanation:

• Python 3.9.0 or Later: The pipe operator (|) utilizes Python's new operator syntax to merge dictionaries.
• Python 3.5 or Later: The double star operator (**) unpacks the dictionaries and merges them into a new dictionary.
• Python 2 and Earlier: The copy() method is used to create a shallow copy of the first dictionary (x) into z, which is then updated with the second dictionary's (y) values using the update() method.

Note:

• The merged dictionary (z) will have the keys and values of the second dictionary (y) overwriting those of the first dictionary (x).
• For recursive merging of nested dictionaries, refer to the accepted answer here: https://stackoverflow.com/a/27181039/17220008

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