Python Error Handling — Junior¶

Use exceptions for exceptional outcomes and make the failure useful.

• Catch the narrowest exception you can handle.
• Add context when re-raising.
• Use finally or with for cleanup.
• Never use a bare except:; it also catches interrupts and system exits.

try:
    user = load_user(user_id)
except FileNotFoundError as exc:
    raise UserNotFound(user_id) from exc

Test both the successful result and the expected failure.