Quick Answer

Safely handle missing dictionary keys.

Understanding the Issue

KeyError occurs when accessing non-existent dictionary keys. Unlike some languages, Python doesn"t return null/None. Explicit handling prevents unexpected failures in data processing pipelines.

The Problem

This code demonstrates the issue:

Python Error 
config = {"theme": "dark"}
print(config["color"])  # Fails

The Solution

Here's the corrected code:

Python Fixed 
# Solution 1: get() with default
color = config.get("color", "light")

# Solution 2: setdefault
color = config.setdefault("color", "light")

# Solution 3: collections.defaultdict
from collections import defaultdict
settings = defaultdict(lambda: "default")
value = settings["missing"]

Key Takeaways

Prefer get() or defaultdict for safe dictionary access.