Apprendre Flexible Decorators

Different functions require a varying number of arguments.

To create a decorator that can be applied to functions with varying numbers of arguments, you can use the *args and **kwargs as arguments in the wrapper() function.

Let's create an indicate decorator that prints information about the function execution:

Print a message that the function has started execution.
Print the arguments taken by the function.
Call the function and save the result that is returned by the function.
Print a message that the function has finished execution.
Return the result.


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def indicate(func):
    def wrapper(*args, **kwargs):
        print("=" * 5,"Func execution starts:", func)
        print("Taken arguments:", *args, kwargs)
        result = func(*args, **kwargs)
        print("=" * 5, "Func execution ends:", func)
        return result
    return wrapper


@indicate
def add_two(a, b):
    return a + b

@indicate
def add_three(a, b, c):
    return a + b + c

@indicate
def add_many_kwargs(**kwargs):
    string = ""
    number = 0
    
    for key, value in kwargs.items():
        string += key
        number += value
    
    return (string, number)

print("Returned:", add_two(14, 21), "\n")
print("Returned:", add_three(225, 12, 11), "\n")
print("Returned:", add_many_kwargs(first=51, second=11, third=47, fourth=93))

The indicate() has the wrapper() that takes the *args and **kwargs. That means that wrapper() can take every number of arguments and keyword arguments.

The add_two() function takes 2 arguments.
The add_three() function takes 3 arguments.
The add_many_kwargs() takes a different number of keyword arguments.

The indicate() decorator can be used for every function.

So, the *args and **kwargs in the wrapper() allow us to use the decorator for any function.

Note

Remember to unpack the received args and kwargs using asterisks (* for args and ** for kwargs) when passing them to a nested function.
If you don't understand or have forgotten how to do this, feel free to come back here.

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Section 3. Chapitre 3

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