How to Merge Dictionaries Using ** Operator in Python

You can merge dictionaries in Python by using the ** operator inside a new dictionary literal, like {**dict1, **dict2}. This creates a new dictionary containing all keys and values from both dictionaries, with later keys overwriting earlier ones if duplicates exist.

Syntax

The syntax to merge dictionaries using the ** operator is:

• {**dict1, **dict2, ...}: Creates a new dictionary by unpacking all key-value pairs from each dictionary.
• Each **dict unpacks the dictionary's items into the new dictionary.
• If keys repeat, the value from the last dictionary with that key is used.

python

merged_dict = {**dict1, **dict2}

Example

This example shows how to merge two dictionaries using the ** operator. The second dictionary's values overwrite duplicates from the first.

python

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

Output

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

Common Pitfalls

Common mistakes when using the ** operator to merge dictionaries include:

• Trying to merge non-dictionary types, which causes a TypeError.
• Expecting the original dictionaries to change; the ** operator creates a new dictionary and does not modify the originals.
• Not realizing that keys in later dictionaries overwrite earlier ones silently.

python

wrong = {**['a', 'b']}  # Raises TypeError because list is not a dict

# Correct way:
d1 = {'x': 1}
d2 = {'y': 2}
merged = {**d1, **d2}  # Works fine

Quick Reference

Summary tips for merging dictionaries with ** operator:

• Use {**dict1, **dict2} to merge into a new dictionary.
• Later dictionaries overwrite earlier keys if duplicated.
• Works in Python 3.5 and later.
• Original dictionaries remain unchanged.

Key Takeaways

Use {**dict1, **dict2} to merge dictionaries into a new one in Python.

If keys repeat, the value from the last dictionary is kept.

The original dictionaries are not changed by this operation.

Only dictionaries can be unpacked with **; other types cause errors.

This method requires Python 3.5 or newer.