Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.python > #89440

Re: Function decorator having arguments is complicated

Show all headers | View raw

On 04/27, Makoto Kuwata wrote:
> 
> I feel that function decorator having arguments is complicated,
> because three 'def' are nested:
> 
>   def multiply(n):
>     def deco(func):
>       def newfunc(*args, **kwargs):
>         return n * func(*args, **kwargs)
>       return newfunc
>     return deco

When I have to write an argument-taking decorator, I use a class:

    class multiply(object):  # don't need 'object in 3.x'

        def __init__(self, n):
            self.n = n

        def __call__(self, func):
            def newfunc(*args, **kwargs):
                return self.n * func(*args, **kwargs)
            return newfunc

>   @multiply(4)
>   def f1(x, y):
>     return x+y
> 
>   print(f1(2, 3))   #=> 20  (= 4 * (2+3))

This all works the same.
> 
> 
> If function decorator notation could take arguments,
> decorator definition would be more simple:
> 
>   def multiply(func, n):
>     def newfunc(*args, **kwargs):
>       return n * func(*args, **kwargs)
>     return newfunc
> 
>   @multiply 4      # ex: @decorator arg1, arg2, arg3
>   def f1(x, y):
>     return x+y
> 
> 
> How do you think about this idea?

It's unnecessary, just use a class instead of a function to get more
clarity.

--
~Ethan~

Back to comp.lang.python | Previous | Next | Find similar | Unroll thread

Thread

Re: Function decorator having arguments is complicated Ethan Furman <ethan@stoneleaf.us> - 2015-04-26 21:24 -0700

csiph-web