从装饰器的“推”属性到Python中的装饰函数

Question

Some basic question from beginner. Is there a way to "push" attribute to a decorated function not using function arguments ?

import sys
from functools import wraps


def decorator_(func):
    @wraps(func)
    def newfunc():
        func.some_attr = 'some_attr'
        func()
    return newfunc

@decorator_
def decorated_function():
    # ??? access some_attr ???
    print some_attr

def main():
    decorated_function()

if __name__ == '__main__':
    sys.exit(main())

Thanks in advance.

Answer 1

Depending on whether you use Python 2 or 3 you can inject variables into the globals of a function like this:

Python 2

func.func_globals["some_attr"] = "some_value"

Python 3

func.__globals__["some_attr"] = "some_value"

Answer 2

If you set the attribute on new_func instead, you can access it simply as decorated_function.some_attr :

def decorator_(func):
    @wraps(func)
    def newfunc():
        newfunc.some_attr = 'some_attr'
        func()
    return newfunc

@decorator_
def decorated_function():
    print(decorated_function.some_attr)

Otherwise, wraps makes the original function available as decorated_function.__wrapped__ in Python 3:

def decorator_(func):
    @wraps(func)
    def newfunc():
        func.some_attr = 'some_attr'
        func()
    return newfunc

@decorator_
def decorated_function():
    print(decorated_function.__wrapped__.some_attr)

In Python 2, the __wrapped__ is not set by wraps , so we need to set it up manually:

def decorator_(func):
    @wraps(func)
    def newfunc():
        func.some_attr = 'some_attr'
        func()
    newfunc.__wraps__ = func
    return newfunc

However, this sounds like an XY problem; if you want to pass a value to the decorated_function you should let decorator_ pass it as an argument instead.