How to check if a function is decorated with a specific decorator?

Question

I want to check if a Python function is decorated, and store the decorator parameter in the function dict. This is my code:

from functools import wraps

def applies_to(segment="all"):
    def applies(func):
        @wraps(func)
        def wrapper(*args, **kwargs):
            func.func_dict["segment"] = segment
            print func.__name__
            print func.func_dict
            return func(*args, **kwargs)
        return wrapper
    return applies

But looks like the dict is lost:

@applies_to(segment="mysegment")
def foo():
    print "Some function"


> foo() # --> Ok, I get the expected result
foo
{'segment': 'mysegment'}

> foo.__dict__ # --> Here I get empty result. Why is the dict empty?
{}

You're modifying the wrong function, at the wrong time. – user2357112 Aug 04 '17 at 22:15 — user2357112, Aug 04 '17 at 22:15
Should I modify "applies" function at run time? – Jorge Arévalo Aug 05 '17 at 09:34 — Jorge Arévalo, Aug 05 '17 at 09:34

score 8 · Accepted Answer · answered Aug 05 '17 at 09:57

8

Ok, thanks to user2357112's clue, I found the answer. Even with an improvement

from functools import wraps

def applies_to(*segments):
    def applies(func):
        func.func_dict["segments"] = list(segments)
        @wraps(func)
        def wrapper(*args, **kwargs):
            return func(*args, **kwargs)
        return wrapper
    return applies

Thanks!

answered Aug 05 '17 at 09:57

Jorge Arévalo

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In Python 3 the `func_dict` attribute has been renamed to `__dict__`. You also need to change the `*segments` to `**segements` in order to use `@applies_to(segment="mysegment")`. – martineau Mar 11 '22 at 15:01

How to check if a function is decorated with a specific decorator?

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