How do you read environment variables using `os.environ` and `os.getenv()`? What is the difference?

• os.environ["VAR"]: Directly accesses the environment variable dictionary. If "VAR" is missing, it raises a KeyError and crashes.
• os.getenv("VAR", default): Safely queries the variable. If missing, it returns None (or the specified default value) without crashing.

import os

# Safe check with fallback value
db_port = os.getenv("DB_PORT", "5432")