Quick Answer

Combine two dictionaries into one.

Understanding the Issue

Python offers multiple dictionary merging approaches with different behaviors for duplicate keys. The update() method modifies in-place, while newer Python versions (3.5+, 3.9+) provide cleaner syntax for creating new dictionaries.

The Problem

This code demonstrates the issue:

Python Error 
defaults = {"color": "red", "size": "medium"}
user_prefs = {"color": "blue"}
-- Need {"color": "blue", "size": "medium"}

The Solution

Here's the corrected code:

Python Fixed 
-- Method 1: update()
config = defaults.copy()
config.update(user_prefs)

-- Method 2: Dictionary unpacking (Python 3.5+)
config = {**defaults, **user_prefs}

-- Method 3: Merge operator (Python 3.9+)
config = defaults | user_prefs

Key Takeaways

Python 3.9+ provides the cleanest merging syntax with | operator.