[FIXED] How to get the decorator handle arbitrary arguments

Issue

I am trying to understand decorators. I want to define a decorator that can handle any arbitrary argument. I am trying the following:

def a_decorator_passing_arbitrary_arguments(function_to_decorate):
    def a_wrapper_accepting_arbitrary_arguments(*args,**kwargs):
        print('The positional arguments are', args)
        print('The keyword arguments are', kwargs)
        function_to_decorate(*args)
    return a_wrapper_accepting_arbitrary_arguments

This is based on this tutorial and it supposedly handles any type of argument. However when I pass only keyword arguments I get the following output with function f(a,b,c):

@a_decorator_passing_arbitrary_arguments
def f(a,b,c):
    print("The arguments here are the following: {0}, {1}, {2}.".format(a,b,c))

f(a='ali', b='emma', c='t')

The output:

The positional arguments are ()
The keyword arguments are {'a': 'ali', 'b': 'emma', 'c': 't'}

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-3-cc5ee8d7120a> in <module>
----> 1 f(a='ali', b='emma', c='t')

<ipython-input-1-af03800e2abd> in a_wrapper_accepting_arbitrary_arguments(*args, **kwargs)
      3         print('The positional arguments are', args)
      4         print('The keyword arguments are', kwargs)
----> 5         function_to_decorate(*args)
      6     return a_wrapper_accepting_arbitrary_arguments

TypeError: f() missing 3 required positional arguments: 'a', 'b', and 'c'

How can I avoid getting this error in the case when all the variables are passed as keyword arguments?

Solution

You are currently only passing on the positional arguments, not the keyword arguments as well, to the wrapped function.

def a_decorator_passing_arbitrary_arguments(function_to_decorate):
    def a_wrapper_accepting_arbitrary_arguments(*args,**kwargs):
        print('The positional arguments are', args)
        print('The keyword arguments are', kwargs)
        # function_to_decorate(*args)  # Wrong
        return function_to_decorate(*args, **kwargs)  # Right
    return a_wrapper_accepting_arbitrary_arguments

(You should also return whatever function_to_decorate returns from the wrapper.)

Answered By - chepner