054-speed-calc-decorator/docs/wiki/Step-2-Decorator-Skeleton.md

Step 2: the decorator skeleton

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A decorator is a function that takes a function and returns another function. This skeleton only announces the call:

def skeleton(function):
    @functools.wraps(function)
    def wrapper(*args, **kwargs):
        print(f"calling {function.__name__}")
        return function(*args, **kwargs)

    return wrapper

Run it with python -m speed_calc.lecture_steps 2.

What we gained

• Functions are values: you can pass them to other functions and return them.
• The inner wrapper is a closure; it remembers function after skeleton has returned.
• *args, **kwargs let the wrapper accept the arguments of any function and pass them on.
• functools.wraps keeps the original name and docstring, so the decorated function still says fast_function.
• @name above a function is shorthand for function = name(function).