Decorators with Parameters

Decorators with parameters in Python are an advanced feature that allow you to pass additional arguments to your decorators, enhancing their flexibility. Here's a practical example to illustrate this concept:

Basic Decorator Structure

First, let's start with a basic decorator structure:


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def simple_decorator(func):
    def wrapper():
        print("Something is happening before the function is called.")
        func()
        print("Something is happening after the function is called.")
    return wrapper

@simple_decorator
def say_hello():
    print("Hello!")

say_hello()

In this example, simple_decorator is a regular decorator that modifies the behavior of the say_hello function.

Decorator with Parameters

Now, let's create a decorator that accepts parameters:


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def decorator_with_args(arg1, arg2):
    def decorator(func):
        def wrapper(*args, **kwargs):
            print(f"Decorator args: {arg1}, {arg2}")
            return func(*args, **kwargs)
        return wrapper
    return decorator

@decorator_with_args("hello", 42)
def print_numbers(a, b):
    print(a + b)

print_numbers(10, 5)

In this example, decorator_with_args is a decorator factory that accepts parameters (arg1, arg2) and returns the actual decorator (decorator). The wrapper function is the one that modifies the behavior of the decorated function (print_numbers).

Explanation

decorator_with_args is called with its arguments ("hello", 42);
It returns the decorator function;
decorator takes a function print_numbers and returns the wrapper function;
wrapper has access to both the arguments of decorator_with_args and the arguments of print_numbers.

This structure allows for greater flexibility and reusability of decorators, as you can pass custom arguments to modify their behavior.

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Seção 5. Capítulo 4