Exercise 1: Basic Singleton with __new__

Goal

Implement a basic Singleton for application settings.

The object represents runtime configuration for one running application process. Different parts of the application may call AppSettings(), but they should all receive the same object.

What you will practice

• Using __new__ to control object creation
• Returning the already-created instance on later calls
• Guarding __init__ so it does not reset state every time
• Checking object identity with is

Starting point

Open exercise1.py.

You are given an AppSettings class and tests. Fill the TODOs so that:

1. AppSettings() always returns the same object.
2. The first initialization wins.
3. Later calls do not reset environment, debug, or features.
4. Feature flags changed through one reference are visible through another reference.

Expected behavior

settings1 = AppSettings(environment="development", debug=False)
settings2 = AppSettings(environment="production", debug=True)

assert settings1 is settings2
assert settings2.environment == "development"
assert settings2.debug is False

The second call should not create or reinitialize a new settings object.

Run the tests

python -m pytest exercise1.py