Serious Python by Julien Danjou

Author:Julien Danjou
Language: eng
Format: epub, azw3, pdf
Publisher: No Starch Press
Published: 2018-12-31T16:00:00+00:00

wraps: A Decorator for Decorators

It can get tedious to use update_wrapper() manually when creating decorators, so functools provides a decorator for decorators called wraps. Listing 7-6 shows the wraps decorator in use.

import functools

def check_is_admin(f):

@functools.wraps(f)

def wrapper(*args, **kwargs):

if kwargs.get('username') != 'admin':

raise Exception("This user is not allowed to get food")

return f(*args, **kwargs)

return wrapper

class Store(object):

@check_is_admin

def get_food(self, username, food):

"""Get food from storage."""

return self.storage.get(food)

Listing 7-6: Updating our decorator with wraps from functools

With functools.wrap, the decorator function check_is_admin() that returns the wrapper() function takes care of copying the docstring, name function, and other information from the function f passed as argument. Thus, the decorated function (get_food(), in this case) still sees its unchanged signature.

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