Apa iku decorator lan papriye carane nulis siji?

Question

Accepted Answer

A **decorator** yaiku fungsi sing **mbungkus fungsi liyane** kanggo nambah perilaku, tanpa ngowahi kode asline. Iki diterapake nganggo sintaks `@decorator` ing ndhuwur fungsi — cara sing bersih kanggo nambah cross-cutting concerns kaya logging, timing, caching, utawa access control.

## Papriye decorator bisa ndadak

```python
def my_decorator(func):
    def wrapper(*args, **kwargs):       # wraps the original function
        print("before")
        result = func(*args, **kwargs)  # call the original
        print("after")
        return result
    return wrapper                       # return the wrapped version

@my_decorator
def greet(name):
    print(f"Hello {name}")

greet("Ann")
# Output: before / Hello Ann / after
```

Sintaks `@my_decorator` yaiku gula kanggo `greet = my_decorator(greet)` — iku ngganti `greet` karo `wrapper`, sing nglakokake kode ekstra ing samubarine panggilan asline. `*args, **kwargs` ndadake wrapper bisa gumana kanggo simbol fungsi apa wae.

## Conto praktis: timing

```python
import time, functools

def timed(func):
    @functools.wraps(func)        # preserves func's name/docstring (important!)
    def wrapper(*args, **kwargs):
        start = time.perf_counter()
        result = func(*args, **kwargs)
        print(f"{func.__name__} took {time.perf_counter() - start:.3f}s")
        return result
    return wrapper

@timed
def slow_task():
    time.sleep(1)
```

`@functools.wraps(func)` penting — tanpa iku, fungsi sing dibungkus bakal ilang ngaran asline lan docstring-ne.

## Decorator karo argumen

```python
def repeat(times):               # outer takes the decorator's argument
    def decorator(func):
        @functools.wraps(func)
        def wrapper(*args, **kwargs):
            for _ in range(times):
                func(*args, **kwargs)
        return wrapper
    return decorator

@repeat(times=3)
def hello(): print("hi")  # prints "hi" three times
```

Decorator sing parameterized kudu perlune lapis tambahan (fungsi sing bali decorator).

## Decorator built-in / library sing umum

```text
@property            → turn a method into a computed attribute
@staticmethod / @classmethod → method types
@functools.lru_cache → memoize results
@app.route("/")      → web framework routing (Flask)
@pytest.fixture      → test fixtures
```

## Apa gunane

Decorator yaiku fitur sing kuat lan khas-Pythonic kanggo **nambah perilaku sing bisa diowahi maneh** (logging, timing, caching, authentication, validation, routing) menyang fungsi kanthi bersih lan deklaratif — misahin cross-cutting concerns saka logika utama.

Iki ana ing mana-mana ing Python nyata: web framework (`@app.route`), caching (`@lru_cache`), kelas (`@property`), lan testing.

Ngerteni papriye cara nulis decorator (fungsi wrapper, `*args/**kwargs`, `functools.wraps`) lan bentuk parameterized ndadake sampeyan bisa nggunakake decorator ekosistem kanthi bener lan mbangun abstraksi sing bisa diowahi maneh dhewe.