KeyError: Missing Dictionary Key

Why This Happens

Accessing a dictionary with dict['key'] raises KeyError if the key is not present. Unlike JavaScript which returns undefined, Python dicts raise an exception.

The Problem

user = {'name': 'Alice', 'email': 'alice@example.com'}
print(user['username'])

The Fix

user = {'name': 'Alice', 'email': 'alice@example.com'}
print(user.get('username', 'N/A'))

Step-by-Step Fix

1. 1

   Use .get() with a default

   Replace dict['key'] with dict.get('key', default).

2. 2

   Check key existence

   Use 'key' in dict before accessing.

3. 3

   Inspect the dictionary

   Print dict.keys() to see available keys.