Different keys
Input
merge_dicts({'a': 1}, {'b': 2})
Output
{'a': 1, 'b': 2}
Both keys are kept; the resulting dictionary has keys 'a' then 'b'.
Full lesson preview
Merge two dictionaries
Combine two dictionaries into one, with the second dictionary's values overwriting duplicate keys from the first.
Python practice6 minDictionaries & SetsBeginnerLast updated March 18, 2026
Problem statement
Given two dictionaries, create and return a new dictionary that contains all key-value pairs from the first and second dictionary. When a key appears in both dictionaries, the value from the second dictionary should overwrite the value from the first. Do not modify the original input dictionaries.
Task
Write a function that returns a new dictionary containing keys from both input dictionaries. If the same key exists in both, the value from the second dictionary should be used.
Examples
Input format
Two Python dictionaries passed as arguments to merge_dicts(d1, d2).
Output format
A single Python dictionary that is the merged result.
Constraints
Both inputs will be dictionaries. Keys are hashable. Preserve insertion order: keys from the first dictionary should appear first (unless overwritten), followed by any new keys from the second dictionary.
Samples
Sample 1
Input
merge_dicts({'a': 1, 'b': 2}, {'b': 3, 'c': 4})
Output
{'a': 1, 'b': 3, 'c': 4}
Key 'b' is present in both; the value from the second dictionary (3) overwrites the first. Key order is 'a', 'b', 'c'.