Dekoratari ni nini na jinsi gani ya kuandika moja?

Question

IT Interview Practice · Accepted Answer

A **decorator** ni funksyon inayofunga funksyon nyingine ili kuongeza tabia, bila kurekebisha kod ya asili. Inatumiwa na sintaksi `@decorator` juu ya funksyon — njia safi ya kuongeza wasiwasi wa kuvuka midSection kama kurekodi, muda, hifadhi, au udhibiti wa ufikaji.

## Jinsi dekoratari zinavyofanya kazi

```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
```

Sintaksi `@my_decorator` ni sukari ya `greet = my_decorator(greet)` — inabadilisha `greet` na `wrapper`, ambayo inaendesha kod ya ziada karibu na simu ya asili. `*args, **kwargs` hufanya wrapper ifanye kazi kwa chochote cha saini ya funksyon.

## Mfano wa vitendo: muda

```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)` ni muhimu — bila hiyo, funksyon iliyofungwa inapoteza jina lake la asili na docstring.

## Dekoratari wenye hoja

```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
```

Dekoratari iliyoongezwa parameter inahitaji tabaka la ziada (funksyon inayorudisha dekoratari).

## Dekoratari za kawaida zilizojengewa ndani / maktaba

```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
```

## Kwa nini ni muhimu

Dekoratari ni sifa yenye nguvu, ya kipekee-Python kwa **kuongeza tabia inayoweza kutumika tena** (kurekodi, muda, hifadhi, uthibitisho, uthibitisho, uelekezaji) kwa kazi kwa njia safi na kitambo — kutenganisha wasiwasi wa kuvuka midSection kutoka logiki ya msingi.

Ziko mahali pa Python halisi: fremu za wavuti (`@app.route`), hifadhi (`@lru_cache`), madarasa (`@property`), na upimaji.

Kuelewa jinsi ya kuandika (funksyon ya wrapper, `*args/**kwargs`, `functools.wraps`) na fomu ya parametrized hukuruhusu kutumia dekoratari za ecosystem kwa usahihi na kujenga abstraksi zako mwenyewe zenye tena.

Jinsi dekoratari zinavyofanya kazi

Mfano wa vitendo: muda

Dekoratari wenye hoja

Dekoratari za kawaida zilizojengewa ndani / maktaba

Kwa nini ni muhimu

Maswali yanayohusiana