Class used as a decorator

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Accepted Answer

When you use a class as a decorator, Python calls the class with the function: greet = CountCalls(greet). greet is now a CountCalls instance, not a function. Calling greet() invokes __call__ on that instance, which increments self.count and delegates to the original function. There are exactly two greet() calls before the print statement, so count is 2. print(greet.count) reads the attribute - it does not call greet. Classes are a natural fit when your decorator needs to maintain state across calls. Instance attributes give you a clean place to store that state, compared to the list-trick or nonlocal workarounds needed in closure-based decorators.