Python Decorators that can Take Parameters

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What if you want the decorator to be able to take an parameter? Let’s create a “num_times” decorator that when applied will run the wrapped function “n” number of times.

Before we do this, as review (read previous tutorial), we write a basic decorator “num_times” that does not take any parameters. It would look like this …

def num_times(orig_func):
    def wrapper(*args, **kwargs):
        orig_func(*args, **kwargs)
    return wrapper

@num_times
def say_hello(name):
    print("Hello " + name)

say_hello("World")

And it would print “Hello World” once.

We would like it to print “Hello” four times when called like this…

@num_times(4)
def say_hello(name):
    print("Hello " + name)

say_hello("World")

Since the decorator num_times take a parameter, we need a additional layer of a “decorator generator” nesting like this…

def num_times(n):
    def decorator_function(orig_func):
        def wrapper(*args, **kwargs):
            orig_func(*args, **kwargs)
        return wrapper
    return decorator_function

The num_times is like a decorator generator. The parameter “n” passed into there is now available for use by the inner functions. We use it in a loop in line 4 below…

def num_times(n):
    def decorator_function(orig_func):
        def wrapper(*args, **kwargs):
            for _ in range(n):
                orig_func(*args, **kwargs)
        return wrapper
    return decorator_function

@num_times(4)
def say_hello(name):
    print("Hello " + name)

say_hello("World")

And it prints “Hello World” four times as expected.

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