What is a class-based decorator pattern?

Question

Accepted Answer

**Class-based decorator** uses a class to implement the decorator pattern. Useful for maintaining state.

```python
import functools

class CountCalls:
    def __init__(self, func):
        functools.update_wrapper(self, func)
        self.func = func
        self.call_count = 0

def __call__(self, *args, **kwargs):
        self.call_count += 1
        print(f"Call #{self.call_count} to {self.func.__name__}")
        return self.func(*args, **kwargs)

def reset(self):
        self.call_count = 0

@CountCalls
def say_hello(name):
    return f"Hello, {name}!"

say_hello("Alice")  # Call #1 to say_hello
say_hello("Bob")    # Call #2 to say_hello
print(say_hello.call_count)  # 2
say_hello.reset()            # Reset counter
```

**Class-based vs function-based:**
- **Class**: better for stateful decorators.
- **Function**: simpler for stateless ones.
- Both use `@decorator` syntax.

Python: What is a class-based decorator pattern?