02_conditionals.py

"""
Small examples demonstrating conditional branches (if / elif / else).

This module shows two short examples using conditionals:
- classify_age: decide what message to return based on an integer `age`.
- tired_response: map a simple yes/no answer into a helpful message.

The functions are written to *return* strings so they are easy to test
and reuse. The `main()` function handles user input and prints results.
"""


def classify_age(age: int) -> str:
    """Return a short classification message for the given age.

    Notes about the conditional logic here:
    - The order matters: checks are evaluated top-to-bottom, so more
      specific conditions go first (e.g., age < 18).
    - We use `elif` to chain mutually exclusive branches; `else` is the
      final fallback when previous conditions were not met.

    Args:
        age: integer age (expected >= 0, but negative values handled)

    Returns:
        A human-readable message describing the age group.
    """
    if age < 0:
        # Defensive check - negative ages don't make sense in this example.
        return "Age cannot be negative."
    if age < 18:
        return "You are a minor."
    elif age < 21:
        return "You are an adult but not 21 yet."
    else:
        return "You are 21 or older."


def tired_response(answer: str) -> str:
    """
    Interpret a user's yes/no input and return an appropriate message.

    This function demonstrates checking membership in a tuple of valid
    options and shows a friendly fallback for unrecognized answers.

    Args:
        answer: user-provided string, expected "y"/"n" or "yes"/"no" (case-insensitive)

    Returns:
        A helpful short message depending on the input.
    """
    normalized = answer.strip().lower()
    if normalized in ("y", "yes"):
        return "Consider going to bed earlier tonight."
    elif normalized in ("n", "no"):
        return "Nice, keep the momentum going."
    else:
        return "I did not understand that, but remember to listen to your body."


def main() -> None:
    """Interactive entry point for the example program.

    This function collects input from the user, calls the pure helper
    functions above, and prints their returned messages. It also shows
    a small example of input validation and graceful error handling.
    """
    raw_age = input("Enter your age: ")
    try:
        age = int(raw_age)
    except ValueError:
        # Input wasn't a valid integer — show an error and stop.
        print("Please enter a valid integer for age (for example: 24).")
        return

    # call the pure function and print its result — this makes testing easier.
    print(classify_age(age))

    tired_input = input("Are you tired? (y/n): ")
    print(tired_response(tired_input))


if __name__ == "__main__":
    main()